Hey Vignesh!
I would start by saying that you need to complete your 12 board exam with maths and physics to be eligible for the Indian airforce.
If you have completed your 12 exams with maths and physics intact then you are eligible to write the NDA exam.
The NDA exam is conducted for all the three branches of defense namely airforce, navy and army.
The age limit should be 16 to 19 years and should be an unmarried male.
Wish you all the best for your future endeavors!