Hello Vishal Kumar,

For Age eligibility proof they might ask for your 10th/ 12th Marksheet or any Government Proof where your complete date of birth is mentioned.

Candidates must have completed 12 th standard or equivalent exam from a recognised Board for Indian Army and Physics and Mathematics is compulsory subjects for Indian Air Force and Naval.

For NDA 2 - 2022,candidates must have born not earlier than January 2, 2004, and not later than January 1, 2007.

For NDA 1, candidates should be born not earlier than July 2, 2003 and not later than July 1, 2006.

To get more information go through below given link.

https://competition.careers360.com/articles/nda-eligibility-criteria

Hope this information was helpful to you.

Best of Luck!!