Hello student!!

Hope you are doing great, as per your query I would like to inform you that NDA is a National level defense entrance examination conducted by Union Public Service Commission - UPSC. If you wish to appear to National Defence Academy - NDA entrance exam your age should be in range of 16.5 years to 19.5 years as on the month of examination.

There is no criteria for number of attempts so yes, if your age lie between the given age criteria you can give as many attempts you wish to.

Hope it helps!!!!