M.Sc Mathematics

You can do M.Sc in any of the private colleges recognised by certain universities without writing entrance test.

Dear Khafeel!
For the entry level post as a TGT-PGT in CBSE School, you need at least B.Sc. Degree. It's a gateway to get into. But If you are having some past 4-5 years of teaching experience in maths already at some other schools than there is very high chances to get the job as a teacher in CBSE S

Yes, it is very much required.

Yes, this course is offered by Gujarat University.

Yes, you are eligible to take admission in many institutions. The cut-off for M.Sc. in Mathematics is 50% aggregate. But in some colleges, you have to take an entrence exam. You can check the best colleges near to your location here:
Shiksha. Com.

Unfortunately, since you have done B.Tech in Instrumentation and control engineering, you do not qualify. You need to be a B.Sc in mathematics and computer education, or any other degree that has math and or computer education. But, you can do it now. So, do it if you really want to get into M.Sc Ma

After completing M.Sc, you can either take a job as a professor or can study further, complete Ph.D and then work as a mathematician and enter in the research field. Many organizations and companies require mathematicians even you can work with the government in the government organisations like ISR