[0ripkindle]

I confess, I did try this method on impulse. It didn't work (gave me an application error) and then I typed ;exit_demo and rebooted. But now I can't turn off airplane mode (I need to registed my kindle once so I get all features. Probably never will turn airplane mode off after, ever). It says:

Feature Locked
This is a managed device. Aeroplane Mode and Bluetooth are locked. For information, contact: Your System Administrator.

EDIT:
Managed to factory reset device, wi-fi works now.

Followed this from OP:
create an empty file named "DO_FACTORY_RESTORE" at the root of the Kindle storage. Once this has been created, reboot the device.