Excuse me, OPPOR 15 system has been updated, how to restore to the previous system?

The mobile phone system supports updating the old system version, but the underlying system may be modified in the process of updating the mobile phone. If you want to downgrade the mobile phone system version, it is recommended that you back up your mobile phone data (phone number, SMS, photos, etc.). ) and bring the mobile phone, purchase invoice and warranty card to the nearest OPPO customer service center for engineers to handle. Thank you for your cooperation.

note:

Android 10 and above models do not support system degradation, please understand.