I'm sorry, but I think there is a misunderstanding. The goal of the jam is to make something during the jam time, and the jam hasn't started yet. It will begin in 21 hours, after which you have a week to make the game. Additionally, when the jam start we will also reveal a theme.
you can, but it is not recommended as it is one of the rating criteria. You are also supposed to make the majority of the game during the jam, which this doesn't sound like.