Science

Yes, you can choose it to do B.Ed in Maths.

Yes, you can have a look at the University of Sikkim, which provides degree through distance mode, and then easily can get the degree. There are number of universities.

For Maths honors, you will study:Calculus
Advance calculus.
Abstract algebra.
Real analysis
Linear programming
Linear algebra.
Differential equations.

Yes, you can pursue Masters in photography and journalism after your graduation is completed.

There are universities which are offering this course:
All the good and reputed universities take entrance exam, group discussion and personal interview.
Entrance Exam usually consist Questions on:
English language Comprehensions.
General knowledge.
General Awareness.
Reasoning.
And,
Media/Journalism Apti

Sorry to disappoint you but Its very difficult to get admission in PUSA with this rank in general category. But there are several other colleges you can try for.

Hello,
There are different exams conducted by well known institutes like IITs-
1) IIT JAM Biotechnology
2) BITS
There are different governmental exams after graduation like SSC CGL, UPSC & Other state government exams.

I will suggest you to study BA because in civil service exam, most of the questions are coming from the areas like history, geography, current affairs, politics etc. It's better to improve your standard/base through studying B.A.