My advice is this. If you are stuck on a question, don't waste your time on it. Just skip it and come backI'd actually suggest a slightly different approach. If you get stuck on a question, before moving on enter your best guess for the answer, and use the 'Mark' capability to mark the question. Then if you have time at the end of the test go back and take a second look at all of your marked questions. This way, if you don't end up having time to go back, at least the question will have been answered. Unanswered questions are automatically wrong. If you take a stab at it, you have at least a chance of having gotten it correct.
later if you have time left. You are better off by answering questions you are certain about the answer
rather than spend a lot of time over a question you are not sure about.