I have to agree that every single topic is important. Actually I have not faced at least one single question in a mock exam that will face just one concept. It is really not about how many topics you know but how and if you really understood them. Then there is also a "thing" that just knowing all the concepts will not get you through the exam. You have to do A LOT of
testing and mock questions, to get a feel on the exam really. I can give you a simple example : I have faced a question where there was a lot of Threading/Serialization going on (you will see that this stuff takes some coding to do - I had to press the exhibit and scroll because the question was pretty big), while going through the logic, I have totally misses that a Date object that was used was never imported.
Do i know that you have to import it? (the concept) - of course, but I have missed that. So just read ALL of the concepts from scratch even if you know them.
Thank you,
Eugene.