You Can Try iOS 9.2 Beta and Return to iOS 9.1/iOS 9.0.2
Developers have already singled out some iOS 9.2 beta 1 problems and we expect the list to grow in the hours, days and weeks ahead. This is early software and it's not for everybody.
If you download the iOS 9.2 beta and you're frustrated with its performance and bugs, know that you can drop back down to iOS 9.1 and, for the moment. iOS 9.0.2.
You'll always have a way to drop back down to the most recent version of iOS 9. So if you're already on the latest version, you can try iOS 9.2 beta without any penalty.
Just remember that you can't drop to anything older than iOS 9.0.2 without jailbreaking your device.