Hey! He shouldn’t have to join the jam, as it’s set to ‘Submitters and Contributors’ can vote. As you submit your entry, you should be able to list your friend as a Contributor and allow him to vote that way!

Happy Jamming! :D

Yes! As long as they are created within the time limit, that's no problem! :D

Anything available through itch.io, that means WebGL, Download for Windows, Mac, Linux, etc., and any other forms of safely sharing projects! :D

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)

Any language is okay, but be aware that majority of the audience will be English-speakers! :)

By the way I don't have discord (and can't get discord).

I'm going to bed but here's the link anyway https://salmoneer.itch.io/side-switch

yes but you need to write down what you have changed in the project's description

I don't think that's a problem. I have seen several of these in other jams, and I didn't see any rule against this so probably its fine