
So the issue so far is we don’t know whether Sungyeon is genuinely smart and only the uke wasn’t aware of it or the teacher/school/Sungyeon’s parents pulled some strings to get him to #1.

Nope. He is getting good grades to be acknowledged by his abusive family. Why would a scumbag and abusive family like his would want to help him by bribing the school to make him get good grades when they don't care about him and just beat him? Don't you remember what his sister said about getting good grades to be acknowledged by their parrnts? He, indeed, did lie to Jiwook to tutor him so he could get closer to him causing his grades to drop.
Choi Kang and Dunno had the most interesting background/foundation. Sad that they were left vague. Or maybe that is part of their charm.