TIFR - Tata Institute of Fundamental Research Mumbai Answered Questions

You are eligible to become an astronaut as you had science stream in 12th class.
Astronaut Eligibility
- You must have passed Ph.D in Astrophysics, Geophysics, Metaphysics from a recognized university.
- You are required to clear entrance exam.
- Your age should be below 21 years.
Steps to Become An Astronaut
- Apply for master's in physics or aerospace engineering.
- Apply for Ph.D in Astrophysics, Geophysics, Metaphysics, Aerospace.
- Apply for entrance of ISRO and clear it with good score.
- If qualified, You will be called for interview.
- If Selected, You will get posting as an astronaut.
Skills Required For Astronaut
- Curiosity
- Great Concentration
- Enthusiasm
- Intelligence
- High Imagination
- Persistence
- Problem Solving Skills
- Analytical Skills

Please refer to the link provided below for details regarding the TIFR exam for various Ph.D. courses offered by Tata Institute of Fundamental Research. Important details like eligibility, application process, exam pattern for this exam is mentioned at this link. Regards. https://www.shiksha.com/university/tata-institute-of-fundamental-research-mumbai/exams/tifr-gs.

No dear, this is not possible to do class 12th with Commerce, and then do B.Sc. So, you have to repeat class 12th with science stream, because both the streams are completely different from each other. And, B.Sc in physics is again a difficult one. But, if you are sure now to change your stream, then you must pursue class 12 with science again.
Yes, most importantly please think twice before taking any step, as it is about your whole life. Your single decision can change your entire life, so please make sure that you must be clear with what you are doing.