I'm pretty sure you can, have a look at last year's games and you can find a couple of games that share assets. The main goal of this jam should be the story and puzzle design, or at least last year it was, given how specific the theme was :D
Yes, that's correct. As stated in the rules, you can use any assets you have the right to use. So if they are free to use or you paid for those assets from the store and thus have a license to use them, you can use them in this jam. Be sure to obey all the licenses for the assets. If they require you credit the creator, you have to do that.
