Bill, it depends on which loop you're in, as Oetkb described.

Yes, in specific loops at septic times of the day. I believe the web site for that National Park lists the loops and times.

I don't have a generator but I just googled the question. here's the policy: Quiet hours are 10pm - 8am. Generators cannot be used during these hours.

In about half of the sites. As I recall there are six loops. Two of of them are "generator free". Quiet hours are 10pm to 8am. See here: Gros Ventre Campground information

Only in the RV loop.

This is an old question, but I wanted to update the answers... For the upcoming 2022 camping season, the campground will be reservations ONLY. No walk-ins. That means even if there are vacancies, they will not allow walk-ins, we'll have to see how strictly they enforce that. As for generator use, there are actually 8 total loops (one is a group loop), and generators can only be used in Loops A, B, and C. Always check their website for updated information. https://www.recreation.gov/camping/campgrounds/247661

Yes, but it depends on which side of the campground you are at. During registration they will ask you.