I2P for Android follows the same release schedule of as the I2P Desktop application. There are three "Official" places to get I2P for Android. The big difference between each platform is how you get updates.
With the Google Play downloads, you'll get updates from Google automatically, usually about 6 hours after I upload them to Google Play Store.
With F-Droid, new updates become available when I upload them to the downloads server, which usually takes about 20 minutes to an hour.
When using a Freestanding APK, you'll need to update the application manually.
Browser Configuration instructions are also on the I2P Site
You'll need to get a browser which can use I2P as well. There are several browsers for Android but almost all of them are quite difficult to configure safely and correctly.
Instructions for Revolution IRC are also on the I2P Site
Revolution IRC F-Droid Downloads
BRB for Android Freestanding APK Downloads
Another, free-standing BiglyBT client tutorial is here: