I'll give you my side
1) Practices were everyday before/after school, either one, not both. Usually Varsity was before and JV after. There was no such thing as a freshman team for us. If you were good enough, you can be on Varsity as a freshman, if not, you're JV. Most varsity swimmers also swim in local clubs, they have daily practices as well...so for some of those people, they get up at 5 in the morning, swam club for 2 hours and swim at school for another 2...I didn't do that though, not dedicated enough to the sport.
2) HS meets are usually one every 1-2 months. School invitational, city championships, etc. Then there are regionals and nationals coming in the spring. Varsity compete more than JV just because they are better. Clubs host meets just as frequently. They can be held at different schools or the swimmer's own school depending on the meet and who is hosting it. Nationals are usually held away at a university swim center, maybe at the state capital.
3) Yes, boys and girls are together. It's a co-ed sport, but obviously boys and girls compete separately.
4) We had about 2 hours of pool time per day (Friday's were shorter), and twice a week we'd be in the weight room or track in the mornings, after that we'd still swim, but not as long.