Definitely agree that you should revise everything, it's just going to be more stressful if you go into the exam hoping the one thing you studied wont come up. That said our teacher didn't cover Global Governance with us because he said it was just asked. Questions about polarity are very popular, the last exam had a short question about multi polarity and one that was basically asking if the current world order was chaotic (anarchic multi polarity). So any questions on polarity would probably be about uni polarity or bipolarity. My teacher focused on "Is China a superpower?" (45) because he thinks its likely. On the EU we spent a lot of time on whether the EU was becoming a federal superstate. IMO a short question about enlargement could also be likely but it's also really essential to the recent development of the EU so make sure you understand the post 2004 developments and the implications.