Hello aspirant!

If you have filled up OBC, that is not a problem. You get chances to correct the form after it's submission. The form is released again in case you have submitted something wrong. Then you can change your category. If this doesn't happen, you will anyways be required to present yourself with a caste certificate and if you fail to do so, you will automatically be considered in the general category. I hope this information was helpful!

I wish you all the very best!