Depending on how many topics you've learnt from PYB4, you could choose 3 topics to revise in a lot of detail, but then in the exam, that limits you to those 3 questions. For example our teacher has taught us 2 topics from child development and 3 topics from atypical behaviour. As you have to answer one question on child development and one question on your option topic, then learn the two you feel most comfortable with, then learn another topic from either child development or the option for your third question, but as i say, that limits the choice of question you can answer.
You can do that on PYB5 aswell for the 2nd question, you choose either a question about debates OR the scientific approach. For the debates question, you have to learn like 5 debates, whereas the scientific approach question, you only need to know the is psychology a science stuff and the role of scientific enquiry etc. But again, just revising for the scientific approach question will limit your choice.