Tested on oppo F1F_EX_11_A.16_160922
Files
Recovery Mode
power + volume down
Unlock Bootloader
flash magictricks.zip using stock recovery
TWRP
flash twrp-3.2.1-0-f1f.img from fastboot
Stock ROM
Downgrade using this file [firmware27]F1F_EX_11_A.16_160922.7z