Hi Omkar,

There is eligibility of Nationality .

Age limit and Marital status 

Candiadte those who are studying 12th ate eligible to apply.

Very important Physical Qualifying .

Syllabus :: 

NDA 1 is purely based don Mathematics there is no change in that from previous year paper.

General Ability - :::part A - english:: part B- G. K

Specific subject section ....

very important please go through this link 

It give you full detail about the above mentioned sections....

https://collegedunia.com/exams/nda/eligibility

Thanks

NDA draws approximately 5 lakh test takers every year but only a few get admission to the prestigious defence academy. The competition is tough therefore it is necessary to take each step in the right direction. In order to prepare for NDA, you must

• Make a routine
• Then start with the basics as it will help in solving the toughest questions without much difficulty
• Solve previous years’ question papers
• Give equal attention to all sections
• And at the end, stay positive

For more details about preparation tips - Check Here