Most questions are answered in our Rules & FAQ on the jam page…
Making Things
All game-specific code, audio, and art assets must be created by you and your team during the jam period. You may use pre-existing fonts. Any game engine features and code libraries for general utilities are also allowed.
What can I work on before the jam?
You are allowed to set up your tools and your game engine. Tools include: palettes, fonts, tracker instruments and code libraries. Anything that is specific to a particular idea should wait until the jam starts.