Hi,
A person is eligible for nri qouta when -
1- passed senior secondary examination with last 2 years comprising of science subjects and english at a level prescribed by ncert.
2. Obtained a minimum of 50% in individual subjects like chemistry, physics, biology, English.
3. Age criteria - completed 17 years of age at the time of admission or will complete the age before 31 dec 2019 and upper age limit is 25 years .
And also to be eligible for nri quota candidate must satisfy the defination of nri as stated in income tax act of 1961.
Hope it helps....