In the presentations, the last portion of the interviews, you need to provide a working demo and defend it against a group of individuals who will question you on it. It's ok to say I don't know, do not make things up because they will immediately fail you based on such. You are much better off saying you need to research and get back to them or you need to engage X to help you with that as you want to provide the proper answers. It's basically role playing. I did learn if you don't have a working demo or one they approve of, the interview is pretty much over.
