The OPPO mobile phone system supports flashing back to the old system version, but since the bottom layer of the system may be modified during the phone flashing process, if you want to downgrade the phone system version, it is recommended that you back up your phone data (phone number, text messages, photos, etc.), take the phone, purchase invoice and warranty card to the nearest OPPO customer service center, and an engineer will handle it for you. Thank you for your cooperation.