If you cleared CTET in 2018 under the OBC-NCL category, that certificate remains valid for eligibility as long as CTET validity rules allow it. However, for KVS PRT recruitment, your category is decided based on your current OBC-NCL status, not the one you had in 2018. Since you mentioned that
The question in the application form can definitely be confusing, but the meaning becomes clear when you break it down. When they ask “In case of girl candidate, are you the only girl child of your parents?” , they are not asking whether you are the only child in the