Dear Devendra, there are 2 things to it.

If you have selected OBC while filling in the NEET application form but now you want to secure a seat under General Category, you cannot. You cannot change your Category in the middle of a process. When you are called in for document verification, not showing your OBC Certificate doesnt put you in General Category. Instead it will be considered as a malpractise and your admission will stand cancelled.

But if you have selected General Category during filling the applucation form though you belong to OBC, then you will be considered under General Category and that doesnt need any documented proof.