Hiya! So in the discord server I've answered this question on the faq page:
Can you start early/use premade assets?
Short answer, no, you cannot start early, but you can use some premade assets. It is a jam so most of it must be made in the time given, however there are certain generic assets, such as a character controller, or some normal 3d models/2d sprites, which you can use, but you must credit the creator of these in your project/itch page. (If it is not you!)