: Power off your phone and insert the SD card.

via SD card" process work, ensuring your device gets a fresh start. Why Flash Your Go to product viewer dialog for this item. via SD Card? No computer required.

Browse the files on your memory card and tap on the firmware .zip file you transferred earlier.

Navigate to the root directory and select the Oppo A57 firmware .zip file you copied earlier.

: You cannot downgrade to a version with a lower security policy than what is currently on the device.

Insert your MicroSD card into a computer or another working phone.