The officially reached its end-of-life support at Android 6.0 (Marshmallow). To upgrade an Oppo F1s to Android 7.1.2 (Nougat) , users must rely on custom ROMs like LineageOS 14.1, as there is no official firmware download for this specific version. Prerequisites for Installation
A full system backup is critical as this process wipes all data. Oppo F1s Firmware Download 7-1-2
Before attempting to flash a custom Android 7.1.2 firmware, ensure you have the following: The officially reached its end-of-life support at Android 6
The phone's bootloader must be unlocked to allow custom software. Oppo F1s Firmware Download 7-1-2
Power off the device, then hold Volume Down + Power simultaneously until the recovery menu appears.