I am taking your 2 question as 1 answer them collectively you have asked for your age and nda eligibility on platform here is your answer

If your date of birth is 22-1-2007, as of today (December 13, 2023), you would be 17 years old in june this is the month of age calculation. And for The NDA ELIGIBILITY CRITERIA you need age between 16.5 to 19.5 years, with a relaxation of six months for SC/ST candidates if you belong to them you get extra years to prepare.

Since you are 16 now you are eligible for NDA exam you could apply for and go through the complete selection process while still studying in 12th class. Approximately 30–40 days (exact date will be in the notification) before the date as it calculate age in june.  you should have proof of passing 12th class and able to submit it to the UPSC or the Indian Army.

If your date of birth is 22/1/2007 then your age as of 13/12/2024  should be 17 years 10 months and 22 days . You will be 18 years in the next month that is jan 2025 . You can verify your age with the help age calculator which are easily available online .