Science

Hello Anil,
The total fee of this course at UEI Thiruvananthapuram is around 1.90 lakhs for 3 years. Please check here for more details.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.shiksha.com/college/amp/uei-global-thiruvananthapuram-36358&ved=2ahUKEwjI2bvYi4fhAhVhguYKHUpZApAQFjACegQIBBAB&usg=AOvVaw0Fgw8DRF9401xvCMtv77jV&cf=1&cshid=1552754111636
All the best.

Hello Harshini Raj,
Please refer to the official website of CUSAT where you may get previous year questions, however, I will suggest you purchase a previous years questions book which is readily available in the market.

Opt for M.Sc in medical microbiology. It has a good scope.

Yes surely you can pursue after doing your Bsc. The best colleges for this course are:
Tamil Nadu Agricultural University Coimbatore
Jawaharlal Nehru Krishi Vishwa Vidyalaya
Mewar University
Lovely Professional University Punjab
Anna University
Acharya Ngranga Agricultural University Hyderabad
Govind Ballabh Pant University of Agriculture and Technology, Pantnagar
Mahatma Phule Krishi Vidyapeeth Puneoknete
Mohanrao Kadam College of Agriculture Sanglisardar.

Delhi University, IPU and some private universities like Amity University are the good options to pursue B.Sc.

If you have good grades in 12th, you will easily get admission there. Just calculate your best 4 and check whether you are eligible for the courses by seeing the cut-off on the DU official website (or check if any entrance test is there for the courses you have mentioned, on the official website of DU).
The fee is very less since they are government colleges.

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

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.