B.Sc

Yes sure you can do the MCA after the B.Sc course. Those students who have done the 12th class or graduation with the math subject then they are eligible to apply. The admission in the MCA course is through the entrance exam which is conducted at the national & state level every year.
If you have good command on the programming language then you should move on this side otherwise not.

At the time market is very bad so if u take admission u have to work very very hard.

go for ABM, it has lot of banking job's
have a look at VGU Jaipur

B.Sc astrophysics combines the two subjects physics and chemistry to study space science, i. e. the birth, life, death of all celestial bodies in the universe. Astronomy and cosmology are the two shoots of it. To study astrophysics, you need to be extremely research and detail oriented with passion to explore. Mhrd started with institutes like IISER to encourage students to take the research path and is doing quite well. You can look for the dual degree program on astrophysics at
http://www.iiseradmission.in/
If you get through, this will be the best choice.
Hope this suffice.

Yes.ofcorse.you can apply and get into the college.you are eligible.

if u are interested in commerce then bca is best or if u are interested in pcm then bsc is the best