Hello, candidates who had completed their Graduation in any field and even the candidates who are in the final years of their Degree Course and have yet to pass the final year Degree examination are also eligible to apply for it. 

In detail.   

• I.M.A. and OTA: Degree of a recognized University or equivalent.
• Indian Naval Academy (INA):  Degree in Engineering from a recognized university/institution.
• Air Force Academy: Degree of a recognized University (with Physics and Mathematics at 10+2 level) or Bachelor of Engineering

For more questions comment below. 

Good luck. 

To write CDSE , the necessity of BSC depends on your choice of service , if you want to serve in the Navy or the Airforce then yes you must have studied BSC with maths and physics. However it is not necessary for IMA and OTA , you can apply for both the academies if you habeha bachelor's degree in any stream from a recognised university.