i have two questions about the game jam:one can you use music from other GB/GBC games? And two what would happen with the prizes if multiple people worked on the game would the person who submitted the game get the prize or would be selected by random?

You can use assets, but if it's from an old official game and you don't have the permission to use the music, it wouldn't be ok.

If a team wins the prize, the person submitted would get contacted, of course.
Might be a good idea to discuss with the teammates internal who would want to take it, if that happens.
The other team members can have a free sticker pack send to each of them, if wanted. (Same pack as place 5-10 will recieve.)

ok thx for the information