diff --git a/packages/react-dom/src/__tests__/ReactDOMFiber-test.js b/packages/react-dom/src/__tests__/ReactDOMFiber-test.js
index efc605a9edb3a..ef872dfeb47e0 100644
--- a/packages/react-dom/src/__tests__/ReactDOMFiber-test.js
+++ b/packages/react-dom/src/__tests__/ReactDOMFiber-test.js
@@ -13,8 +13,6 @@ const React = require('react');
 const ReactDOM = require('react-dom');
 const PropTypes = require('prop-types');
 
-const ReactFeatureFlags = require('shared/ReactFeatureFlags');
-
 describe('ReactDOMFiber', () => {
   let container;
 
@@ -249,7 +247,7 @@ describe('ReactDOMFiber', () => {
   });
 
   // TODO: remove in React 17
-  if (!ReactFeatureFlags.disableUnstableCreatePortal) {
+  if (!__EXPERIMENTAL__) {
     it('should support unstable_createPortal alias', () => {
       const portalContainer = document.createElement('div');
 
diff --git a/packages/react-dom/src/__tests__/renderSubtreeIntoContainer-test.js b/packages/react-dom/src/__tests__/renderSubtreeIntoContainer-test.js
index 2a540f9929d14..678f96de9f080 100644
--- a/packages/react-dom/src/__tests__/renderSubtreeIntoContainer-test.js
+++ b/packages/react-dom/src/__tests__/renderSubtreeIntoContainer-test.js
@@ -19,7 +19,7 @@ const renderSubtreeIntoContainer = require('react-dom')
 const ReactFeatureFlags = require('shared/ReactFeatureFlags');
 
 // Once this flag is always true, we should delete this test file
-if (ReactFeatureFlags.disableUnstableRenderSubtreeIntoContainer) {
+if (__EXPERIMENTAL__) {
   describe('renderSubtreeIntoContainer', () => {
     it('empty test', () => {
       // Empty test to prevent "Your test suite must contain at least one test." error.
diff --git a/packages/shared/ReactFeatureFlags.js b/packages/shared/ReactFeatureFlags.js
index 400ace66c99c6..bdd6cc9a6c057 100644
--- a/packages/shared/ReactFeatureFlags.js
+++ b/packages/shared/ReactFeatureFlags.js
@@ -44,10 +44,6 @@ export function addUserTimingListener() {
 // Disable javascript: URL strings in href for XSS protection.
 export const disableJavaScriptURLs = false;
 
-// These APIs will no longer be "unstable" in the upcoming 16.7 release,
-// Control this behavior with a flag to support 16.6 minor releases in the meanwhile.
-export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
-
 // Warns when a combination of updates on a dom can cause a style declaration
 // that clashes with a previous one https://github.com/facebook/react/pull/14181
 export const warnAboutShorthandPropertyCollision = true;
@@ -107,10 +103,6 @@ export const runAllPassiveEffectDestroysBeforeCreates = false;
 // WARNING This flag only has an affect if used with runAllPassiveEffectDestroysBeforeCreates.
 export const deferPassiveEffectCleanupDuringUnmount = false;
 
-// Use this flag to generate "testing" builds, that include APIs like act()
-// and extra warnings/errors
-export const isTestEnvironment = false;
-
 // Enables a warning when trying to spread a 'key' to an element;
 // a deprecated pattern we want to get rid of in the future
 export const warnAboutSpreadingKeyToJSX = false;
@@ -127,22 +119,14 @@ export const warnAboutStringRefs = false;
 
 export const disableLegacyContext = false;
 
-// Disables hydrate, render, findDOMNode, unmountComponentAtNode
-export const disableLegacyReactDOMAPIs = false;
-
 // Disables children for <textarea> elements
 export const disableTextareaChildren = false;
 
 // Disables Maps as ReactElement children
 export const disableMapsAsChildren = false;
 
-// Disables ReactDOM.unstable_renderSubtreeIntoContainer
-export const disableUnstableRenderSubtreeIntoContainer = false;
 // We should remove this flag once the above flag becomes enabled
 export const warnUnstableRenderSubtreeIntoContainer = false;
 
-// Disables ReactDOM.unstable_createPortal
-export const disableUnstableCreatePortal = false;
-
 // Modern event system where events get registered at roots
 export const enableModernEventSystem = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.native-fb.js b/packages/shared/forks/ReactFeatureFlags.native-fb.js
index 787ebbb602e25..2a6d0c93962be 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-fb.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-fb.js
@@ -24,7 +24,6 @@ export const enableSchedulerTracing = __PROFILE__;
 export const enableSuspenseServerRenderer = false;
 export const enableSelectiveHydration = false;
 export const enableBlocksAPI = false;
-export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
 export const warnAboutShorthandPropertyCollision = true;
 export const enableSchedulerDebugging = false;
 export const debugRenderPhaseSideEffectsForStrictMode = true;
@@ -44,15 +43,11 @@ export const disableLegacyContext = false;
 export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
 export const enableTrainModelFix = true;
 export const enableTrustedTypesIntegration = false;
-export const disableLegacyReactDOMAPIs = false;
 export const disableTextareaChildren = false;
 export const disableMapsAsChildren = false;
-export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
 export const runAllPassiveEffectDestroysBeforeCreates = false;
-export const isTestEnvironment = false;
 export const enableModernEventSystem = false;
 export const warnAboutSpreadingKeyToJSX = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.native-oss.js b/packages/shared/forks/ReactFeatureFlags.native-oss.js
index 6dece82d185f2..1aa8be179cb3c 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-oss.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-oss.js
@@ -23,7 +23,6 @@ export const enableSelectiveHydration = false;
 export const enableBlocksAPI = false;
 export const disableJavaScriptURLs = false;
 export const disableInputAttributeSyncing = false;
-export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
 export const warnAboutShorthandPropertyCollision = true;
 export const enableSchedulerDebugging = false;
 export const enableDeprecatedFlareAPI = false;
@@ -39,15 +38,11 @@ export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
 export const enableTrainModelFix = true;
 export const enableTrustedTypesIntegration = false;
 export const enableNativeTargetAsInstance = false;
-export const disableLegacyReactDOMAPIs = false;
 export const disableTextareaChildren = false;
 export const disableMapsAsChildren = false;
-export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
 export const runAllPassiveEffectDestroysBeforeCreates = false;
-export const isTestEnvironment = false;
 export const enableModernEventSystem = false;
 export const warnAboutSpreadingKeyToJSX = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.persistent.js b/packages/shared/forks/ReactFeatureFlags.persistent.js
index f3c3c0a506917..4ec1c8ed30f8e 100644
--- a/packages/shared/forks/ReactFeatureFlags.persistent.js
+++ b/packages/shared/forks/ReactFeatureFlags.persistent.js
@@ -23,7 +23,6 @@ export const enableSelectiveHydration = false;
 export const enableBlocksAPI = false;
 export const disableJavaScriptURLs = false;
 export const disableInputAttributeSyncing = false;
-export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
 export const warnAboutShorthandPropertyCollision = true;
 export const enableSchedulerDebugging = false;
 export const enableDeprecatedFlareAPI = false;
@@ -39,15 +38,11 @@ export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
 export const enableTrainModelFix = true;
 export const enableTrustedTypesIntegration = false;
 export const enableNativeTargetAsInstance = false;
-export const disableLegacyReactDOMAPIs = false;
 export const disableTextareaChildren = false;
 export const disableMapsAsChildren = false;
-export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
 export const runAllPassiveEffectDestroysBeforeCreates = false;
-export const isTestEnvironment = false;
 export const enableModernEventSystem = false;
 export const warnAboutSpreadingKeyToJSX = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
index af95e4ecc7ccd..c1fae8355a973 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
@@ -23,7 +23,6 @@ export const enableSelectiveHydration = false;
 export const enableBlocksAPI = false;
 export const disableJavaScriptURLs = false;
 export const disableInputAttributeSyncing = false;
-export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
 export const warnAboutShorthandPropertyCollision = true;
 export const enableSchedulerDebugging = false;
 export const enableDeprecatedFlareAPI = false;
@@ -39,15 +38,11 @@ export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
 export const enableTrainModelFix = true;
 export const enableTrustedTypesIntegration = false;
 export const enableNativeTargetAsInstance = false;
-export const disableLegacyReactDOMAPIs = false;
 export const disableTextareaChildren = false;
 export const disableMapsAsChildren = false;
-export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
 export const runAllPassiveEffectDestroysBeforeCreates = false;
-export const isTestEnvironment = true; // this should probably *never* change
 export const enableModernEventSystem = false;
 export const warnAboutSpreadingKeyToJSX = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
index 881733ee14957..45bb75b5b9d00 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
@@ -21,7 +21,6 @@ export const enableSchedulerTracing = __PROFILE__;
 export const enableSuspenseServerRenderer = false;
 export const enableSelectiveHydration = false;
 export const enableBlocksAPI = false;
-export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
 export const warnAboutShorthandPropertyCollision = true;
 export const enableSchedulerDebugging = false;
 export const disableJavaScriptURLs = false;
@@ -39,15 +38,11 @@ export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
 export const enableTrainModelFix = true;
 export const enableTrustedTypesIntegration = false;
 export const enableNativeTargetAsInstance = false;
-export const disableLegacyReactDOMAPIs = false;
 export const disableTextareaChildren = false;
 export const disableMapsAsChildren = false;
-export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
 export const runAllPassiveEffectDestroysBeforeCreates = false;
-export const isTestEnvironment = true; // this should probably *never* change
 export const enableModernEventSystem = false;
 export const warnAboutSpreadingKeyToJSX = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.testing.js b/packages/shared/forks/ReactFeatureFlags.testing.js
index 84f2ea701be8d..30ba2e1f35f23 100644
--- a/packages/shared/forks/ReactFeatureFlags.testing.js
+++ b/packages/shared/forks/ReactFeatureFlags.testing.js
@@ -23,7 +23,6 @@ export const enableSelectiveHydration = false;
 export const enableBlocksAPI = false;
 export const disableJavaScriptURLs = false;
 export const disableInputAttributeSyncing = false;
-export const exposeConcurrentModeAPIs = __EXPERIMENTAL__;
 export const warnAboutShorthandPropertyCollision = true;
 export const enableSchedulerDebugging = false;
 export const enableDeprecatedFlareAPI = false;
@@ -39,15 +38,11 @@ export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
 export const enableTrainModelFix = true;
 export const enableTrustedTypesIntegration = false;
 export const enableNativeTargetAsInstance = false;
-export const disableLegacyReactDOMAPIs = false;
 export const disableTextareaChildren = false;
 export const disableMapsAsChildren = false;
-export const disableUnstableRenderSubtreeIntoContainer = false;
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = false;
 export const deferPassiveEffectCleanupDuringUnmount = false;
 export const runAllPassiveEffectDestroysBeforeCreates = false;
-export const isTestEnvironment = true;
 export const enableModernEventSystem = false;
 export const warnAboutSpreadingKeyToJSX = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.testing.www.js b/packages/shared/forks/ReactFeatureFlags.testing.www.js
index 8246883d39cc9..37d53806ff11a 100644
--- a/packages/shared/forks/ReactFeatureFlags.testing.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.testing.www.js
@@ -23,7 +23,6 @@ export const enableSelectiveHydration = true;
 export const enableBlocksAPI = true;
 export const disableJavaScriptURLs = true;
 export const disableInputAttributeSyncing = false;
-export const exposeConcurrentModeAPIs = true;
 export const warnAboutShorthandPropertyCollision = true;
 export const enableSchedulerDebugging = false;
 export const enableDeprecatedFlareAPI = true;
@@ -39,15 +38,11 @@ export const disableSchedulerTimeoutBasedOnReactExpirationTime = false;
 export const enableTrainModelFix = true;
 export const enableTrustedTypesIntegration = false;
 export const enableNativeTargetAsInstance = false;
-export const disableLegacyReactDOMAPIs = __EXPERIMENTAL__;
 export const disableTextareaChildren = __EXPERIMENTAL__;
 export const disableMapsAsChildren = __EXPERIMENTAL__;
-export const disableUnstableRenderSubtreeIntoContainer = __EXPERIMENTAL__;
 export const warnUnstableRenderSubtreeIntoContainer = false;
-export const disableUnstableCreatePortal = __EXPERIMENTAL__;
 export const deferPassiveEffectCleanupDuringUnmount = false;
 export const runAllPassiveEffectDestroysBeforeCreates = false;
-export const isTestEnvironment = true;
 export const enableModernEventSystem = false;
 export const warnAboutSpreadingKeyToJSX = false;
 
diff --git a/packages/shared/forks/ReactFeatureFlags.www.js b/packages/shared/forks/ReactFeatureFlags.www.js
index a1032d3d8d447..5ff790efe4612 100644
--- a/packages/shared/forks/ReactFeatureFlags.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.www.js
@@ -45,8 +45,6 @@ export const warnAboutDefaultPropsOnFunctionComponents = false;
 
 export const enableTrainModelFix = true;
 
-export const exposeConcurrentModeAPIs = true;
-
 export const enableSuspenseServerRenderer = true;
 export const enableSelectiveHydration = true;
 
@@ -95,20 +93,12 @@ export const flushSuspenseFallbacksInTests = true;
 
 export const enableNativeTargetAsInstance = false;
 
-export const disableLegacyReactDOMAPIs = __EXPERIMENTAL__;
-
 export const disableTextareaChildren = __EXPERIMENTAL__;
 
 export const disableMapsAsChildren = __EXPERIMENTAL__;
 
-export const disableUnstableRenderSubtreeIntoContainer = __EXPERIMENTAL__;
-
 export const warnUnstableRenderSubtreeIntoContainer = false;
 
-export const disableUnstableCreatePortal = __EXPERIMENTAL__;
-
-export const isTestEnvironment = false;
-
 export const enableModernEventSystem = false;
 
 // Flow magic to verify the exports of this file match the original version.