IIT Delhi will open its correction window for GATE 2020 applications and you can make changes to your Category. The official website states that the correction window for Category and other fields will open in due course. There has been no date mentioned though. Please watch out for their official notification at: http://gate.iitd.ac.in/index.php . Because you are forgoing a reservation Category, you may have to pay additional fees for the application. Also please visit our page for more information at: https://engineering.careers360.com/articles/gate-application-form-correction