Hello Pritam,

Yes, you are elligible for NISER Examination. This exam requires at least the candidate to be born of 1999. And there is no upper age limit for this exam. You may give this exam as many number of times you want. 

It includes:- 

1) General Section of 30 marks.

2) Biology of 50 marks.

3) Chemistry of 50 marks.

4) Physics of 50 marks.

5) Mathematics of 50 marks.

So you must be opting PCMB in your 11th and 12th standard. The syllabus will be as of NCERT pr as pee CBSE curricullum.

Thank you.