Hello,

You have to fill the correct details in the application form. if you had made any mistake then you will get a chance to correct when correction window opens. for current year, JEE mains application and correction window is already closed.

you can't change details in counselling process registration. if authority finds any mishap then your application form will get rejected.

You can apply for OBC for jee mains. to claim reservation category, you have show official documents. That's all required.

Hope it helps!