Using TWRP, go into command mode and type the command used to turn off the flag to boot into recovery. Should get you back booting on 11A.
If you screwed up and Factory Defaulted, then you'll gonna have to restore stock and update naturally before hacking.
To restore stock, you gotta download the stock TOT file and use the flasher to go back to stock, then update the OTA updates twice up till the latest 12B. RE-Root and reinstall TWRP.
Nothing else works. Not even restoring a backup. The Flasher app was pretty straight forward after downloading all of the DLL files needed to launch it.
Sent from my VS980 4G using XDA Premium 4 mobile app