I typically score high on RC. I do not skip questions. Usually once I've read the question, it's in my mind, so it's time to work on it. As for individual questions within a specific problem, once I can't figure out how to do it right away, I brute force as fast as I can.
And no, there's no time to change your answers right at the last few minutes. The best you can do is just to go and "retry" stuff. Like if it says: All can be true EXCEPT, then go retry the one you circled and if it works, then you know you messed up and you should probably just randomly circle another one sicne you're low on time. You've increased your chances to 25% up from 0%, so that's already pretty good