I have migrated a few apps from 7 to 8 and they work just fine.

I have not tried importing them back to joget 7 so i can't comment on that.

It also depends on the amount of customization that you have performed in your apps. For example, if you use a lot of custom CSS or JavaScript then there might be a possibility that you need to tweak them. 

In terms of moving back, I think it should be fine if you do not use any new features that are specific to the new version. Having said that, in any kind of software deployment you should ALWAYS test changes in a test or staging environment first before attempting to do it in production. And always have backups!

The upgrade seems to be seamless without issue so far. It could be because there is very less customization. Anyway, it is better to test it out before do the migration.   

Thanks all of you for you support.