Kind of a weird question :).
In my understanding a Facebook review (in my case) is to allow my app to use extended permission (ex:user_photos).
Can I submit a basic app that does something simple(ex:upload a picture), submit for review, get validation, then create a totally different app?
Or will I have to resubmit when I make a change to my app?
Or will they scan each apps to see that the app didn't deviate?
I'm just being curious here :).
The answer is here: https://developers.facebook.com/docs/facebook-login/review/faqs#permissions_app_updates
Although, if you change it to something completely different, you need to make sure it is still allowed. Don´t try to get a permission approved just to create something different that would not get the permission approved (just stating the obvious).
Btw, of course the App has to be about something serious, i don´t think you would get anything approved if you just present a very basic functionality without any sign how you want to use the permission later. A simple picture upload form without anything else may not get approved. Just build a basic prototype of your App before submitting.