Indian Institute of Science Education and Research Mohali Answered Questions

That's not how it works. In IISER Pune and IISc, you can't choose your subject before admission. After two years in IISER Pune and three semesters in IISc, you can select your major subjects. Then you'll have to study the courses specified by the respective department; you can choose astrophysics if you have a course. Also, you can do your thesis in astrophysics if you want.

While it's better not compare older IISERs with newer ones, according to 2022 NIRF rankings, IISER Pune, Kolkata, Mohali, and Bhopal are in the overall category. The rest are not mentioned in the overall rankings. Nature Index (overall share): Bhopal, Pune, Kolkata, TVM, Mohali, Tirupati and Berhampur. But I suggest you do not rely only on one particular ranking system as they would have one flaw or the other. Instead, you should SEE the ranking of a specific department in which you are interested, like nature. Don't forget to SEE further details.

You have two ways. First is just after B.Sc. You have two exams: IIT JAM and JEST Physics. You can give both exams. Happens in February every year. Than people who score top ranks in these exams are called for interview in iisc Bangalore. If you clear interview. You will get admission in integrated Ph.D. in iisc. In this you do your M.Sc. And Ph.D. and than leave iisc after 6-7 years. In this you will get 16000rs per month in M.Sc. And 31000rs per month in Ph.D. Second is you do M.Sc. From somewhere else. Than you can give three exams GATE CSIR NET and JEST. Qualify any one of these with top rank. Under 100. Than you will get Interview call. And you will be selected as Ph.D. student in IISc. You will get 31000rs every month.

IISER exam is divided into 4 parts and has 15 questions from Each Subject. Physics - 15 Questions
Chemistry -15 Questions
Maths- 15 Questions
Biology - 15 Questions
No Sectional Cut Offs. It is not compulsory to attempt biology but they will consider its marks in the total I. e. your marks will be out of 180. If you are a PCM Student- You can really do good in PCM Questions + Study NCERT Level Biology).
Thanks!