The tasks are designed so that you can give them a good shot without knowing what exactly they compromise. You may complete it, you may not but as the chaps on here have said that is irrelevant. I have OASC in a couple of months and I just plan to be relaxed and myself. Everyone I have spoken to says that they enjoyed their time at OASC, which is an attitude I've adopted. If I don't pass at least I can make sure I damn well give it my all and enjoy my time there.
Try not to worry too much.