Good questions I hadn't considered. Let's go with:
1. Recognizability is key. Obviously it's more clear if the opening material is repeated exactly with orchestration and harmony, but there isn't a deduction, per se, as long as it's really clear.
2. Same general answer as above, but yes, I don't see why not.
3. I think I answered this actually, but yes, shared material should be at the beginning.