B.Sc

Please refer to this link:
https://www.shiksha.com/science/colleges/b-sc-colleges-patna

No, it's not possible because you chose physics. You can only do M.Sc in the subject which you opted for in B.Tech.

Yes, you can do this course.

Both are good. It depends upon your area of interest. Whether you want to study arts or science. Think before choosing it as it is a life turning situation for a student after class 12. Follow your passion.
All the best.

Hello,
Yes, indeed. But firstly, let me appreciate your desire to continue your studies for PG even if in external mode. Savitribaie University offers many courses to external students who for varied reasons are not able to attend regular classes in college. I am attaching a link that will give you all the required information.
http://app1.unipune.ac.in/external/

Your class 12th percentage is average, so there is a remote possibility to get admission for B.Sc in IT in Raj University under TFWS.

Hi,
You are eligible for this course. It's a two-year full-time postgraduate course divided into two semesters.
Duration-
Minimum: 2 Years
Maximum: 5 years
Eligibility- B.Sc (Home Science) / B.Sc (Applied Nutrition) / B.H.Sc (Rural) / B.Sc (Clinical Nutrition and Dietetics) / B.Sc (Food Science and Quality Control) / B.Sc (with Nutrition/Foods as one paper) / B.H.Sc (Home Science special 4-year course) / B.Sc (Microbiology, Biotechnology, Biochemistry) / B.Sc (BZC).