Checking that thread it looks like a TWRP backup. So what you need to do is go into TWRP, connect the phone to the PC and paste the file into the TWRP folder. Then, wipe /system, /data and the cache partitions with TWRP and then select the "Restore" option, selecting the TWRP backup. Then reboot the phone and see if it boots into Sense. If it does, then your phone is back to stock ROM wise. Go back into TWRP and connect it back up to the PC, and delete the TWRP folder on the phone. Now go into fastboot mode and then with fastboot do the following with the stock reovery you downloaded:
Code:
fastboot flash recovery recovery.img
This will flash the stock recovery, once that's done do:
Now your phone should be fully stock and OTA updates should work as well.