For SHM questions, do you have to derive the formula v2=n2(a2-x2) using acceleration since its not on the reference sheet? Or can you just whip it since its SHM?
Yes you can just use it. Keep in mind that formula sheets were only introduced in like 2013 or so. I only found out last year that there was now a formula sheet lol (and likewise with multiple choice, which was also introduced around the same time).