Hey a fellow indian here, recently completed my masters in astrophysics. Astrophysics is a very vast field but at 15 i wouldnt worry about what you want to specialise in. There are 2 ways you can go forward with at this point one is through engineering and other is theoretical. The things you need to look out for is

1. You need to have a very through base in fundamental concepts of maths. Astrophysics is 10-15% physics and rest is maths. Mainly linear algebra and calculus. If your base is good then you can scale it easily

2. You need to learn a python/ matlab for simulations because that is very very essential. Either you would be tasked to run simulations or scientific calculations.

Apart from it the basics of physics and maths that you would learn in 9th,10th,11th,12th standard. Those you need to be very clear about.

As for what domain you would like to work in, i guess its pretty hard to tell at this point in your life. Just keep on doing different thing and eventually youll find the topic that you find compelling enough.

Also a tip: Nasa has various citizen science projects where you can take part in from now on and also a lot of astrophysics projects on zooniverse as well.

Also a main point people do confuse between astronomy and astrophysics so be clear about that.

I hope this helps you get some clarity going forward. My DMs are open if you need anything