Hi Flogo,
OTA stands for Over the Air and refers to an update that is delivered via the internet. That aside, in the OTA you’ll find the original system, meaning the FP-stock-rom your phone came with. I would assume, that your method should have reverted the OS to the original. I wonder why it didn’t…
What you could try is to use adb sideload to flash the image. That worked for me in any case…
To do that, start into recovery mode and select “apply update via adb”, then connect your phone and use
adb sideload FP2-gms36-1.1.7-ota.zip
to flash the image to the phone…
Hope that works for you!
Moritz