Help needed. Really confused about NIOS

I passed 12th this year with state board with 68 percent which isn't enough for jee. So I thought of giving nios again as a fresher because jee doesn't accept two different marksheets. I called the helpline number to confirm if I can do this thing and it's legal. A month ago one guy said that it's fine but today I called the same official helpline and some other guy said both of your marksheets(the old one and the one you'll get from NIOS) will become invalid.

I really don't know what I should do because this is getting really complex. Also, what if I give nios marksheets for jee and use the old state board marksheets for other exams like mhtcet comedk cuet(asking this so that I'm safe from a disaster in NIOS)