I'm currently in first year. Will giving mains cancel my admission in my college?

Dear Aman
As shefali explained very well,  I just want to add one point that..
You can successfully take JEE Mains test but after getting rank.  You need to quit the college which you're studying now.. Because as you already submitted your original certificates in the college you need to get them for taking admission into any NIT /iit college.  They will give certificates only after paying 4 years college fee.
Make sure that you'll take the correct decision.
All the best.

No, your admission will not cancel if you appear for JEE Main exam.

If you take admission in other college then you have to cancel your admission in present college.

Good Luck!!