I think you need to add the team members as admins to the project page before submitting, but I could be wrong. Best to do that to be sure :) This is the first jam I'm hosting so I am not 100% sure but a quick search tells me you can update the game up until deadline. The project page you create is attached to your itch.io account and stays there as long as you want. The jam results/submissions page stays online as long as the host want :)