Can I repeat Class 12 after passing??

Yes you can repeat 12th as many times as you can. Just be sure that repeating 12 th each time will reduce your chances of getting a seat based solely on 12th marks (such as BCom, BSc or BA) each time. You might get 90% next time or 70 % but keep in time only this new score will remain, the old ones get wiped out.
https://www.ribblu.com/cbse/papers/class-12