If the device won't enter EDL with buttons, you may need to use a test point on the motherboard or an EDL cable.
If you're dealing with a bricked or need to bypass an FRP lock, having the right programmer file is a lifesaver. This firehose file allows tools like Hydra Tool , UnlockTool , or QFIL to talk to the Snapdragon 435 chipset in EDL mode. Model: OPPO A57 (CPH1701) oppo a57 firehose file
format) used to communicate with the device's Qualcomm Snapdragon processor while it is in Emergency Download (EDL) Mode If the device won't enter EDL with buttons,