Generally speaking, as long as you did your project on part II successfully, you will have no problem for part III. What I did is that I submitted my project and read my design in project II and SCEA forum and then assume some potential questions and organize answers. A week later, I took essay exam and I felt that I am very clear and calm in this exam. Well, I found out that I did not answer well for 1 or 2 questions, actually I did well in my design, however it might be language issue causing me misunderstand questions, I changed my mind in the middle of answering essay questions. Well, be confident and you will do well.