Computer Science and Engineering

You need to write an improvement exam for that, as there are less or no chances for getting admission on that basis.

Top Computer Science Engineering Colleges in India Accepting JEE Mains are mentioned at the link provided below:
The ranking is based on engineering ranking published by The Week.
https://www.shiksha.com/b-tech/ranking/top-computer-science-engineering-colleges-in-india-accepting-jee-mains/46-2-0-0-62

Use UPSEE 2018 college predictor to predict the colleges you might get-
https://www.shiksha.com/b-tech/resources/upsee-college-predictor

You might not find it difficult to get admission in private colleges and universities of India. Many small-town colleges take only those who have appeared and won't make it an issue about rank and marks.
You may also apply to private universities like Amity, Manipal, KR Mangalam, CU Mohali, etc.

Hello Snehdeep,
It's indeed nice to see that you are getting admission in Thapar in your desired branch. For becoming an IAS officer, you need to pass civil service exam, for which being a graduate is a must. So if you study well during four years at Thapar, it'll actually add up to preparation for

You will easily get a seat in one of the NITs with higher rank with CSE stream. Kindly fill the counselling form according to your preferences. Moreover, you'll get one definitely in Surathkal, Rourkela, Warangal and Trichy.

Hello,
See, only on the basis of 12th marks, top engineering colleges will not offer seats. You need to either write the entrance exams like KCET or the entrance exams particular to that college.
Else, you can try for management quota.

Hello, with your ranking, it is possible to get a seat in BIT.
For more information on cut-off, you can refer to their website or the college predictors.
Try for it. Good luck.