To be eligible for mht CET you should have 50 percent in combined of all subjects that you have in your class 12th standard.

if you have less than 50 percent you will definitely not going to give examination only students allowed For reserved category with 40 percent.

If you want to repeat 12th you can but it will take your precious years so think before doing that it must contribute to your future goals.

Other thing is if you want to do job in future you can do it by scoring good in your graduation.i suggest you to pass your b.a exam with good marks more than 50 percent that makes you eligible for the most of the masters courses in future in good universities.

Its not necessary to change your past mistakes rather than learn from your mistakes.

Good luck ..