Hello Susmita,

Hope you are doing well.

NIOS is an open schooling board and different MNCs have different guidelines for recruitment. Some may allow open schooling candidates for a job and some may not even consider them for interviews. Hence, you need to apply according to their eligibility criteria.
There is absolutely no problem if you have given 12th board examinations from NIOS board. It will be a problem or not, that depends on company's policy and frankly, the recruiter.
NIOS provides certification which is equivalent to any board certification.
It would be treated equally like central or State board.

Hope this will help you.

Good Luck!