Botany

In-order to get admission in Ranchi University for Post Graduate course in Botany, you have to clear the entrance exam organized by the university.
Admission Eligibility: B.Sc/ B.Sc (Hons.) with 55% aggregate marks.
For More Info please visit: http://www.ranchiuniversity.ac.in/2014-03-31-05-27-00/2014-04-02-06-49-40/botany.html

Please refer to the link provided below for eligibility criteria to pursue M.Sc in Petroleum Geology from The Maharaja Sayajirao University of Baroda.
https://www.shiksha.com/science/course/m-sc-in-petroleum-geology-the-maharaja-sayajirao-university-of-baroda-vadodara-179243

Yes, all biology, physics & chemistry portion of 11th & 12th CBSE board. You can expect many knowledge-based MCQ questions as well.

It depends on college to college. Yes, in prestigious colleges, they take an exam, and in some colleges, they offer you on the basis of your graduation percentage.

Yes, you can apply but you must have mathematics as a subject in your 10+2 course.
Thank you.

You can refer these books for further clarity on the subjects you have chose for entrance exams.
1. Book: M.Sc Biotechnology Entrance Exam Objectives
Author: Kumar P, Arti Gupta, Preeti Tripathi
Guide and practice papers by Prabhanshu Kumar
2. B.D Singh- Plant Tissue Culture.
3. Shular -Bioprocess and Fermentation Tech
4. T.A. brown- Gene Clonning
I hope these books will be helpful. All the best for your exams. Thank you.

Yes, you can opt for M.Sc Botany if you have opted botany as a generic elective course during your B.Sc.