You are welcome. You gave it a valiant effort & did discover some workarounds along the way. Good going though they don't last. The ball is in MSFT's court now. Good luck & keep us informed. Careful on those stairs.
(Hmm, so it isn't strictly a Win 8.1 problem. OK.)
For the record, here is my key...
It doesn't have AllowInsecureGuestAuth at all which normally means it is set to 0 (off).