Hi Bella! I am currently attending FIU (but transferring next semester) and I am going to try to answer your questions as best I can.
1. Admission is not extremely selective. When I did my application I didn't even have to do an essay or send in recommendations. I think the most important part is you GPA and SAT/ACT.
2. Honestly no. I don't recall being asked for volunteer hours, but that doesn't mean you shouldn't do them!
3. A 3.7 is more than good enough. I got an academic scholarship with a 3.6 weighted.
4. There are actually 2 campuses, the main one being Modesto Maidique (south). It's pretty lively and there is always music playing. I don't like that too much so I stay at north (biscayne) campus, which is much quieter. Depends on your personality, really.
5. From Biscayne it's sunny isles. From Modesto I'm not sure, but I know it's not far.
6. Not really. There are a lot of different countries represented, but it is majority Hispanic/Latino (about 65% I think).
7. I'm really sorry, but I can't answer this one. I really don't know. It's probably pretty good though. We have a pretty nice aquatic center it biscayne campus.
Good luck in your college search! Hope I helped!