M.Sc

No, you should have done B.Sc in the same field to do M.Sc afterwards.

Hi Jane,
Candidates can only apply for the course if they are passed with B.Sc. (Physics). Interested candidates can apply online with required information. Admission is based on the marks obtained in graduation.
https://www.shiksha.com/science/course/m-sc-in-physics-women-s-christian-college-college-road-chennai-110549

Yes, you can do M.Sc maths. After the completion of your degree, you can apply for admission. You will get admission.
Good luck.

There are not much chances because they give admission after qualifying entrance exam. So, you cannot get admission there. You should take admission in any other college.
Good luck.

Your question is incomplete as you Haven't mentioned which course you want in MS Ramaiah.
So, with KCET 2544, you can get a seat but CSE, ECE are difficult.
College is around 50-70k (You will get scholarship if you belong to special background) and hostel normal cost around 1 lakh.

What exactly is your question? Please clarify.

Eligibility criteria for M.Sc in Food Science and Nutrition from Mount Carmel College is mentioned below:
B.Sc Home Science or Family and Community Sciences/Clinical Nutrition and Dietetics/Food Science and Quality Control/ Nutrition and Dietetics/B.Sc with Human Nutrition/Applied Nutrition/Food Science and Nutrition/ Clinical Nutrition and Dietetics/ Food Science and Quality Control with a minimum of 50% marks in aggregate from a recognized board or institution.