B.Tech

Firstly, check whether you have received any confirmation mail from NTA. Secondly, check whether you have got any payment confirmation mail from NTA. Thirdly, check the website from which you have applied for. Fourthly, check the NTA website for JEE Mains exam, open the student portal and check there whether you have missed any relevant information or any notification regarding the admit card release or whether your application is accepted. Check when was the date of release of admit card and last date of admit card collection. If you do have a confirmation mail but you still have not received the admit card, report it immediately to the NTA through an e-mail available at the bottom of their webpage for disputes. If the date has passed, then sorry to say, you can not give the examination for the first attempt, but do not worry, I think the registration for the second attempt (April session) of the JEE Mains exam will commence from 3rd February or 7th February for sure and will be open till March beginning. Please do complete your registration carefully this time in the presence of an expert, make your payment properly, check for your confirmation mails. Best of luck, study well.

It depends on your state of domicile and how much financial backing you have .
In state level colleges, you may get CSE with this percentile, with home state quota.
Rajasthan Engineering Admission Process (REAP) , has decent govt colleges at Jodhpur, Kota, Udaipur etc and it also gives admission on the basis of JEE Main. Here 15% seats are for outside candidates. Even 90 percentile in JEE main can fetch you a seat there.
Similarly admission to GGSIP University, Delhi, is by your JEE Main rank. Here there are 3 -4 decent colleges, USICT, MSIT, MAIT etc. Fee is much less, when compared to other private colleges. Your entire B Tech course fee will be 6 - 7 lakh.