instead of OBC category I enter unreserved due to lack of cast validity, can I changed it during counseling round?

Once you have already submitted a category during form fill up you cannot change it later on during the process of verification on counselling from unreserved to other backward classes or any other category even if you have the relevant documents is this was a matter of attend negligence and such negligence will cost you as it is your situation right now and you will have to face it that way and the only option left before you is going in as a non reserved candidate even with your requisite documents present with you since you are not attentive enough to avail it during the time you should have

Dear Aditi, unfortunately you cannot change your Category once after you fill in the application form. Once you click on 'Submit' what you enter there, stays there. And the merit list is prepared by the Category you have chosen while filling in the application form. Last minute changes aren't entertained.