Hi aspirant,

NDA examination conducted by UPSC for entry to Indian armed forces, Indian Air forces and Indian Navy through the National Defense Academy, Pune. Since the examination is held to select the candidates who will run the best armed  forces and have the responsibility of one of the toughest roles there is no type of reservation in the examination. So your friend can apply for NDA irrespective of the caste certificate provided that he/she fulfills the necessary eligibility criteria.

The eligibility of candidates is determined based on multiple factors like age, educational qualification, physical standard, nationality the details for which can be found on the link below: https://competition.careers360.com/articles/nda-eligibility-criteria

Hope it helps!!