jsg How do I roll back the 2.1 app to 2.0?
Look into your tablet for the older APK. Should be there unless you had deliberately deleted it. Just search the web on where to find the APK files. Install the APK that you want.
You also need to roll back the the firmware (to the factory defaults, usually) if you want to roll back the app past the firmware version that is currently installed. The different models of ASIAIR have different ways to do that; the forum is full of posts on how to roll back firmware.
However, there already could be something wrong with the firmware that is in the ASIAIR right now; causing the update to fail. And can cause other firmware updates in the future to fail. It is probably best for you to revert back to the original firmware than came with the ASIAIR from the factory. If you do that, you should also be able to use the firmware that v2.1 needs.
Chen