M.Sc

M.Sc honors is a four year integrated course after class 12th at BITS. Dual degree in BITS means that you can do another higher graduation degree along with M.Sc degree, e.g. M.Sc physics student can do B.Tech ECE as second / dual degree, simultaneously by choosing electives in M.Sc degree from B.Tech syllabus to reduce time period of second degree. In five to six years an average plus student can do both.

Yes, you can.
For more details, you can check the following link:
www.ignou.ac.

For correspondence courses, Sikkim Manipal is the best university.
You can check the below mentioned link for the list of colleges:
https://www.way2college.com/colleges/msc/bangalore

Calcutta University is the best university to pursue M.Sc in geography.

It is not possible to get admission in M.Sc geography after B.Sc mathematics honors. You have to continue with mathematics in M.Sc too.
Best of luck.

It depends on the field, which you study.

Based on market opportunities and scope, my recommendations in order of precedence for M.Sc students are electronics, physics and astrophysics.

After M.Sc biochemistry, there are so many options for job:
1. Pharmaceutical companies in R&D.
2. Research lab.
3. Food companies.
4. Bio fertilizer companies, etc.