Sorry for the delay but let me address your questions:
1) You can simply use the app to backup your programs and settings (on Android). I recommend you use the email export so you have a tangible copy of the data.
2) You can start over with a fresh image instead of having to worry about what to clean and what to keep. This can be done by following the latest instructions: https://opensprinkler.freshdesk.com/support/solutions/articles/5000524845
3) Flow meter support, including logging, is now added in 2.1.6 which will be released soon.