It can be up to 30% prelim work in the exam, I'm pretty sure they can only ask year 11 things in the multiple choice though. I dropped down to general at the end of yr 11, and I just went through the textbook and did one chapter per day (10 days), and for each chapter just made sure I knew or wrote down the formulas, then did every second question from the chapter review.
If you have enough time I suggest doing a similar thing, if you are time limited I would just make sure you know the terms/formulas for anything you don't already know by heart, such as dividend yield and things like that