B.Sc

Apply for DU in June-July when registrations start. It offers B.Sc in Botany and B.Sc in Zoology.

Yes, you can. But, I don't think you can do all the three courses together, because geography doesn't belong to the biological side. But you can do Botany, Zoology and Geology. It will have high value.

You should do B.Sc (Hons) in Botany. It has good future prospects.

Kindly visit the links mentioned below:
https://www.shiksha.com/science/colleges/b-sc-colleges-mumbai-all

After completing your graduation, you can go for M.Sc Zoology, botany and chemistry as per your interest. You can also apply for Diploma course DMLT, MBA, B.Ed (NET, SET - after M.Sc. Or else, prepare for civil services, banks exams and other competitive exams.
Good luck.

As per your background, I would suggest you opt for M.Sc in Biotechnology, whereas, it completely depends upon your interest. I have one of my classmate who did Bachelors in Biotechnology with me and then moved on for Mass communication for Master's degree because of his interest.

Which subjects are you interested in?

Yes, it is necessary for M.Sc to get a degree in the same subject. So, if you want to do M.Sc in botany you have to do B.Sc in the same.

See, to be clear you can't manage both B.Sc and NEET together.
There is a saying that do not put each foot on different boats. So I suggest that do not mess up with 2 different courses. Just be clear about what is your goal, it is either B.Sc or getting MBBS through NEET. But remember one thing, you should be confident about what you want to choose. Your goal should be clear.