I saw it needs to be work you already worked on. But I don't have any work I have done previously that would fit this. Am I allowed to make a project before the jam and send that work when it starts?

No, the purpose of this jam is to finish older projects so that participants can have one less thing to worry about for the main YaoiGameJam event. 

If you wish to start a new project, you are encouraged to join the main event.