1. No. Sports looks to be a pick up and play kind of thing. Like if your bored, you pick up a basketball and shoot or volley a soccer ball (or kick it at someone) or throw a dodge ball at people or practice some boxing to bring yourfighting skills up. Boxing is the only one confirmed as a competition based sport. And although i have seen american football uniforms, there hasnt been any pics of an actual football.
2. At the very start you can just mess around the school until you start the storyline. As soon as you do, the game clock starts. And you can either go to class and follow the storyline or just mess around all day but the teachers and hall monitors willl be after you. Yes you do have to sleep by at least 11pm, afterwords you start getting blurry screens until you pass out at 2am. and wake up really late.
3. I dont really know, but if its anything like GTA then youll have free roam and be able to do (repetitive) side missions where nerds stuff has been stolen etc...
4. You can try, but im guessing he just grabs you and takes you to his office before you do anything good. And when your in his office, its just a cut-scene. (i presume from videos)