Reverting FW:
1) Download version:
https://pgaskin.net/KoboStuff/kobofirmware.html Go bottom of page and click show
2) Unzip the download
3) Connect ereader via USB (make sure at least 50% charged and on Home screen)
4) open two windows: One inside unzip folder and one inside .kobo On Mac & Linux you need to enable view hidden files/folders as a .prefix hides.
5) Copy the unzipped files into the .kobo window/folder/directory
6) Select eject/unmount etc OS command and only eject when OS says, or wait for Kobo Home screen.
7) Unplug USB, the Kobo will be rebooting.
8) Wait till it's all done and homescreen is back. Do not touch power button!
9) Do a power down & restart, then check version in settings.