Resetting the device if you are locked out of the pattern or PIN.
Flashing stock firmware does not SIM unlock a device. You need a network unlock code from OPPO or a third-party service. oppo a57 2016 firmware
This usually means a hardware mismatch or corrupted eMMC storage. Try the SP Flash Tool method. If it fails at 100%, you likely have dead NAND memory. Hardware repair is required. Resetting the device if you are locked out
If you accidentally installed malicious apps that factory reset can’t remove (because they reside in the system partition), a full firmware flash wipes everything clean. oppo a57 2016 firmware
This guide provides everything you need to download and install the Oppo A57 (2016) firmware safely. Why You Might Need This Firmware