CBSE

Hello Anand,
As per your rank, your chances are nil for getting any reputed colleges, however, check here to know more.
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor

You'll have to bring the case to the notice of the collage administration. Its on there discreation.

Hi,
You can use this MHCET college predictor tool
to know the available shortlisted colleges based on your marks:
https://www.shiksha.com/b-tech/resources/mhcet-college-predictor

To get admission in Delhi University in B.Sc mathematics, you should clear your mathematics subject in your 10+2 with 50% and should score more than 40%.

You have to got 75% marks to be in top 20% percentile of college. But nevertheless, you can get admission in NIT-Raipur. But firstly, there is the first requirement. So, you can go for some integrated course in branch selection and then, the internal sliding, you can get the branch as per the requirement.

Hello Akshay,
Please refer to this link to get more insights of colleges and branches:
https://www.shiksha.com/b-tech/resources/mhcet-college-predictor.
However, as per your marks, you will get lower colleges.