How different is Uni from JC?

Hii. Graduated from JC in 2023 and about to enter uni life this year. Was just wondering how drastic of a change uni life is? For instance, 1. the timetables, is it 2 classes per day like poly life? and spread out throughout the day unlike the systematic JC timetables. 2. how are ccas like there too? would u recommend someone to get one cca? and would two be too much? 3. I was wondering how the class dynamic might be too since everyone would be of varying ages. and also any tips from seniors who r in year 2 uni or above would be appreciated :)