I'm gonna take a quick stab at these, but I'd need to get you official confirmation.
1. Yes, I am sure that all changes need to be approved. If not, then you could make a silly app, change it and put in things that are not legal and it would continue to run under the radar until someone mentioned it.
2. I don't see how it could be, but I guess it's possible. I would think it would have to be back in dev to make alterations.
3. Of course! if you change the code and put in something that's against the guidelines, or tos the reviewers would catch it and suspend you and you'd be back to square 1 :)
Like I said, I would need to get confirmation but these are my assumptions :)