I would say you don't want to skip/guess any but you may have to...
I had to guess one on my final exam (guessed wrong by the way) since after 3 mins I still could not solve it. I ended up with Q49, so too bad but ideally, you only want to guess the questions you truly can't answer (vs. running out of time).
I just did a timed SC and I'm really slow (1:30 per question). How do you get to finding the correct answer in under a minute consistently?