Hello Vishnu

Yes you may go for class xii from NIOS and will be allowed for appearing Neet in future years .

NIOS marks are accepted in states of India except Anna university and colleges of Chennai as there syllabus is different.

You have passed class x from kerala but it will make no difference if you will bevwriting your xii board from NIOS.

After qualifying neet you will be also eligible for medical seats.

So not to worry NIOS board is government recognized and nios marks are accepted in most of the states of India except a few.