I don't think I know the real answers but here is what I think:
1. can't answer sorry. I don't understand the question
2. you probably can. I don't think there is any point in doing so (cuz game jams are about making games, and just simply having fun), but I think you can.
3. You can make devlogs about making your game. Advertising is a different story. It depends on where you want to advertise it and you can only do so if the site allows you to do.
4. Probably only the top ten or something. He will probably stream playing them so you can rewatch those (in case youtube/twitch allows rewatching streams)