M.Sc

Hi
For this course, you will have to first complete B.Sc in microbiology. Please check the prospectus of the course provided by the university to get all the details regarding admission procedure, eligibility and syllabus.

The questions are generally based on graduation level. It would be best if you buy 10 years previous year question papers to practice.
Zoology: Eligibility - The minimum eligibility criterion for a student to take admission in B.Sc. Zoology is that the candidate must have studied Physics, Chemistry, and Biology in class 12. The candidate should also have attained a minimum of 50% aggregate in 10+2 examinations.

Hi
This is a good university. Refer the link:
https://www.shiksha.com/university/calcutta-university-Kolkata-24674/reviews
although it is better to do M.Sc. From foreign university. You can clear the exam of IACP which will send you to foreign countries for studying.

Hi,
As per the DRDO's notification no 2019/20-MS, the crucial dated of eligibility is 23rd January 2020 for calculation of age and other eligibility criteria. And after calculation of yours age on 23rd January-2020, your age is 25 years. Which is not meeting the age criteria as defined by DRDO. Hence you can not apply.

Yes, you can definitely go for this because it is a good opportunity for you.

You should go for MCA or MBA. But as if you said you had BCA so I think MCA probably would be best for you. Anyways, it is your career and at last, your choice matters.

Please check the website of the Nalanda Open University to get information about all the study centers.