CBSE 12th

For IITs,you need to qualify JEE Advanced. With JEE main you can get admission in NITs and other private colleges.

Yes, you can pursue.

Let him please choose whatever he is interested in dont coax anything on him otherwise later on he may go haywire and end up doing nothing

Yes, you are eligible for the exam.

Hello Mohd
You Need minimum 5.5 IELTS score to get student visa for Australia
in 12th you should have physics and maths with minimum 75% marks for good university

You can apply with your scores. You would be required to perform well in the PI to be selected for the course. As the selection is based on scores and PI both.

Avinash,
Check the link below to know the colleges that you can get with this rank:
https://www.shiksha.com/jee-mains-college-predictor
Also, using your rank, you can take direct admission in some good private university. These days we have so many good private universities also imparting quality education to the students around the world. They offer you admission on JEE scores/ tests conducted by them/ your marks in 12th. Some of these also offer good scholarships based on any one of the above mentioned admission criteria.
Check the websites of some good universities or call on their toll free number for more details.
Good luck.