Dear,

Eligibility Criteria for engineering admission on the basis of 12th marks is as follows:

1) You must have completed class 12th (10+2).
2) Secured minimum 45-50% marks in higher secondary examinations (12th).
3) Must have studied Physics, Mathematics & English as compulsory subjects in the 12th.
4) Completed 12th from any recognized school by CBSE, ICSE, NIOS, or State Boards.

You need to also appear for entrance exams such as JEE, CET etc. Each university has different entrance exams for B.Tech in their college. I would recommend you to find a university near to your residing place and research on it.

Hope this helps!