B.Sc

You should go for mathematics (Hons.). Yes, BA in mathematics (Hons.) is available.
BA in maths (Hons.) is essentially equivalent to Bachelor of Science or Bachelor of Arts degree with a specialty in mathematics. Relatively, few institutions award Bachelor of Mathematics degrees, and the distinction between those, that do and those that award Page on B.Sc or BA degrees for mathematics is usually bureaucratic, rather than curriculum related. However, schools that offer Bachelor of Mathematics degrees argue for a separate degree, maintaining that the study of mathematics is vastly different from other fields.

Hello Nilesh,
As there are many IT companies in India, there are many opportunities for computer science graduates. The salary for B.Sc computer science graduates may be a little low compared to M.Sc graduates. So, I advise you to do M.Sc computer science after 2-3 years of work experience. Following are some of the careers that I know in the field of Computer and IT:
1) Call Centers,
2) Computer-Aided Design
3) Computer Science Engineer
4) Hardware Engineer
5) Network Engineer
6) Software Engineer
7) Web Designer
8) Web Developer

DRDO publishes requirement of science graduates for the role of research assistants at regular interval. You are advised to look for the next opening at DRDO on their website and apply for the post suitable to your educational background.

JNU does not offer B.Tech or B.Sc degrees. You may refer to JNU e-prospectus:
https://admissions.jnu.ac.in/Default2.aspx#