Using this Google Play Services asset, you can implement:
To use IAPs you will need to also import the Google Play Services IAP asset into your project: http://marketplace.yoyogames.com/assets/4629/google-play-services-iap
1) To be able to build a project with the Google Play Services Extension, you'll need to install the Google Repository: Android Studio > SDK Manager > Android SDK > SDK Tools > Support Repository > Google Repository
2) For logging into Google Play, make sure that you're targeting your own Google Services ID in Game Options > Android > Social. You may also need to upload an APK to Google Play Console before you'll be able to log in to Google Play on your app. When signing into your game via Google Play Services, you must be using an executable that has been signed in the project with the same keystore as the one initially provided to the Google Play Console, otherwise login attempts will be rejected and will return -1.
3) To test Achievements and Leaderboards, you'll need to create your own game on the Google Play Console and create achievements and leaderboards for it. The example code shown for the objects in this extension will help you understand how to then apply your own values later.
Moved notifications functionality to separate extension: https://marketplace.yoyogames.com/assets/8090/google-push-notifications
Fixed some compatibility issues with other Google extensions.