Science

You will be eligible for admission in M.Sc CS in majority of universities. You are advised to prefer M.Sc over MCA as you will be able to save one year. However I will recommend that brand image and placement records of PG institute be main criterion for chosing between degrees.

In biology field you have lots of options to do with. Like MBBS BDS BPharm DPharm B.Sc Nursing Medical Science Biological Science Agriculture Forestry.
MBBS BDS being the most preferred

Please, proceed to the university and contact the HOD. He may provide you with hints. For a scholarship, you have to complete NET/CSIR process. They may be not be given directly by the University. Anyhow, check.

To become astronaut you must do B.Tech Aeronautical Engineering and also obtain Flying license with more than 1000h of flying experience. By the way first astronaut was from Fighter branch of Indian Air Force. There are very limited nearly zero opportunities for astronaut in India. You may able fullfil your dream abroad only.

Some of the best coaching institutes are there like TIME or IMS, etc. They generally provide coaching for MBA but they can give you the best knowledge for bank exams. So, don't wait, grab the opportunity.

It would be a good option.