Prerequisites

Before diving into the implementation, make sure you have the following set up:

A React Native project.
Firebase project with Remote Config configured.
Knowledge of Fastlane and basic understanding of GitHub Actions.

Step 1: Setting Up Fastlane

Initialize Fastlane:
```
fastlane init
```
Follow the prompts to set up Fastlane for your project.
Update Fastfile: Replace the contents of your Fastfile with lanes for both iOS and Android. This file will automate the deployment process.

Step 2: Using Remote Config for Update Checks

Integrate Firebase into React Native: Follow the Firebase documentation to integrate Firebase into your React Native app.
Set Up Remote Config Parameters: Configure a parameter (e.g., minimum_required_version) in the Firebase Console to store the minimum version required for the update.

Fetch Remote Config in Your App: Use the react-native-device-info library to dynamically retrieve the current app version.

import { useEffect } from 'react';
import { Alert, Linking } from 'react-native';
import DeviceInfo from 'react-native-device-info';
import { firebase } from '@react-native-firebase/remote-config';

const App = () => {
  useEffect(() => {
    async function fetchRemoteConfig() {
      await firebase().remoteConfig().fetchAndActivate();
      const minimumRequiredVersion = firebase().remoteConfig().getValue('minimum_required_version').asString();

      // Get the current app version dynamically
      const currentVersion = DeviceInfo.getVersion();

      if (compareVersions(currentVersion, minimumRequiredVersion) < 0) {
        // Show a mandatory update prompt
        Alert.alert(
          'Update Required',
          'A new version of the app is available. Please update to continue using the app.',
          [
            {
              text: 'Update Now',
              onPress: () => {
                // Open the app store for the update
                // Example for opening Google Play Store on Android
                Linking.openURL('market://details?id=com.yourapp.package');
              },
            },
          ],
          { cancelable: false }
        );
      }
    }

    fetchRemoteConfig();
  }, []);

  return (
    // Your app components
  );
};

export default App;

Step 3: GitHub Actions Workflow

Create GitHub Actions Workflow: Set up a GitHub Actions workflow to automate the build and deployment process whenever changes are pushed to the main branch.
Set Up GitHub Secrets: Add necessary secrets (e.g., FASTLANE_USER, FASTLANE_JSON_KEY_DATA) in your GitHub repository settings.
Push Changes: Push the changes to the main branch to trigger the GitHub Actions workflow.

Conclusion

Congratulations! You've successfully set up Fastlane for automating app deployment and integrated Remote Config to enforce app updates. Users will be prompted to update their apps when a new version is available, and the update process will be managed using Fastlane and Remote Config.

By maintaining a single version number and using remote configuration, you've streamlined the update process for both Android and iOS platforms. This approach ensures a consistent and efficient way to deliver the latest features and improvements to your users.

Feel free to customize and expand upon this guide based on your project's specific requirements and configurations.