Export as Cordova
Then turn into APK with Intel XDK
https://www.scirra.com/tutorials/809/ho ... -crosswalk
Intel has two options for Android, Android and Android Crosswalk, you'll need to use Android Crosswalk
To add admob you'll need to add the plugin
It is straight forward to update APK, you just need to increase the 2 versions in the export settings.
I can't confirm the leaderboards, check the plugins while your adding admob or maybe it is ready by default...