Hey there! This is what we mean:
"What do you qualify as "already"?" If you made it BEFORE the Game Jam started on 09/01/2020 then you cannot use it.
"If resources must be shared..." We're not 100% sure what you mean. If you want to share something you created for this Game Jam, then you have to wait until the Jam (up to and including the awards) is completed.
We hope that answers your questions!