The only exception is if you plan on applying for scholarships, in which case you could probably argue that the more shit you list the better, but even then no one really cares; most scholarships are entirely on the basis of academic achievements and/or financial/personal disadvantages.
Definitely not, except courses with an interview or portfolio, etc. Other then that the uni will never know whether you attended or missed school events because firstly they don't have the time to check every single student that has applied whether they attended or not and secondly they don't really care cause that shouldn't define someone's acceptance or decline in a course.
Only atar is considered that's all. I never went to a carnival since yr 9 and I am doing fine.