Air 3.1 Quick questions

Hi,  I created my first app using air 2.7. Everything went well - no bugs. I'm about to release my next app, so I'm wondering whether to update to 3.1.

Is it worth it if I'm just doing basic stuff? Just thinking of the future:

1) if I make an app with 2.7, and later use 3.1 and update it - will apple allow it? May not be compatible for some people who bought the original..

2) is an air app made with 2.7 automatically compatible with iOS 5?

3) has air 3.1 sorted out the localisation problem with all languages listed? The workaround is too fiddly for me..

Thanks,

Matt