Science

You should clear all the graduation years to further pursue your studies. So it is advised that you clear all the back papers if you want to pursue your studies further.

Yes, the college requires 50% marks in class 12th with mathematics the admission will be based on entrance test result followed by the counselling.

Best combination is always the one which is of your interest or according to the career or stream you wish to pursue in future after the completion of your course. You can take mathematics too.

Yes, as per my knowledge you can do B.Ed. It does not need any kind of teaching experience for you to take admission in the course.

Yes, you can get admission in SRM University if you have completed your 10+2 grade with an aggregate marks of minimum 50% or above. Another criteria says that you should have the compulsory subjects that are required for the B.Sc in agriculture course.

Yes, you can do BA programme. There will be deduction in percentage because you are changing your stream.
All the best.

The branch of astronomy concerned with the physical nature of stars and other celestial bodies, and the application of the laws and theories of physics to the interpretation of astronomical observations. I can also send you the list of college with their eligibility criteria if you want.

Here is the list of colleges in Maharashtra that offers B.Sc in agriculture:
https://www.shiksha.com/science/colleges/b-sc-agriculture-colleges-Maharashtra

BHU is a university which takes admission at a very high cut-off. But keep pace with the counselling process till the end. You may secure a seat.