Punjab

Hi,
Cut-off marks varies from college to college, but yes, for a good college, you require a score of 200-220. An even better score like 250-270 will land you in SPA Delhi.

Apply for MNIT-Jaipur.
NSIT and PEC are difficult for you to grab as you are from Rajasthan and belong to OBC category. Try for MNIT-Jaipur, you might get this college easily.

Here, I suggest some good college list DAV, Government Colleges for Girls, Punjab University and SIPT are government colleges in Chandigarh for B.Sc in computer science.

You have to appear in its entrance exam.

The Chandigarh Group of Colleges, Landran, near Mohali is an old name. It is a known institute in that region and has made a good reputation in admissions as well. However, the placements are still a thing to question. Still, in comparison to their own CU, they are far better and good opportunities are possible through MBA.

Yes, you can if your rank is under the required rank for this college.