Thank u sir for ur response but I have few doubts
1) is passing 12 from 2 different boards in different years legal in India
2)JEE advanced can be written only 2 times after completing 12 ie the year of completing 12 and the next year.
So if NIOS is considered this year will be my last year for JEE advanced but if CBSE is considered I will get 2 more years.So can I be able to write JEE next year on the basis of CBSE board and neglecting NIOS board
Thanks in advance

nirupesh Yes its illegal having 12 certificate from 2 boards in same year but legal if you have gap between them . Now you can give JEE if apply using your cbse marksheet & you will get 3 chances of Mains & 2 of Advance counted from the year you pass 12 from cbse & not of nios.

Vishal Chaurasia Hello Mr Vishal Chaurasia. I've a similar query regarding this and I am not getting a definite answer from somewhere. Can you please help me