Science

In my opinion, for CBSE 12th class Chemistry studies, you have to join the best coaching classes, refer to the last 5 years' question papers, etc. Best of luck for your future and if there's any query, feel free to ask.

Yes, your rank is decent. But there are less chances for government colleges.
But you still try for government colleges in the councelling rounds. But you may get good private colleges with this rank.

Initially, you will have to do your graduation in microbiology or zoology and then you can go for research in the field.

Yes, by the entrance examinations held by any university, but you have to score above 50% or 60% according to the requirement of the college.

Yes, it is compulsory to have Maths in 12th and have passed in the subject to be eligible for the honours course. Maths isn't compulsory for the BCom programme. General category requires around a minimum of 97%.

M.Sc. Fashion Designing or Master of Science in Fashion Designing is a postgraduate fashion and interior designing course. Fashion design is the art of the application of design and aesthetics or natural beauty to clothing and accessories. Fashion design is influenced by cultural and social latitude

You score good marks in 12th and must have PCB.

B.Tech has higher value than B.Sc. But. As u say B.Tech has only better value if u finishes it from a better college. So in my viewpoint finish B.Sc. CS from S. R. M and then do a master degree. This will fetch u with good salary package. Good luck!

https://www.shiksha.com/science/course/integrated-b-sc-hons-m-sc-hons-in-mathematics-maharshi-dayanand-university-rohtak-270937
I am sharing a link here. You go through the link here. You will get all knowledge about MDU campus.
Good luck.