So this is my frist Game jam, and I want to know what platform we have to release our game on. Do I have to do the operating system that I am running, or do I have to make it available on everything, from Windows to a Chromebook?
You may build for any platform. From the FAQ:
No specific platform or engine is required! But the more platforms the more people can play your game. Typically web based games will be played more.