While I understand you're doing your best to help, I'm really pissed that Garmin does not admit this cockup and does not immediately push a fixed firmware version.
But do the readings change over time? As far as I remember, previously, when altimeter/barometer issue happened, it was possible to make it display the current numbers, but they would never update afterwards.
I note the advice on making a back-up (to restore settings after a reset). I'm holding back on that at present (lack of confidence that I'd be able to restore completely without significant messing about). I have noticed that if you can get passed the initial lock-up (e.g. by holding down the GPS button to initiate a fix), it is then possible to initiate an activity and control it as normal. The lock-up only happens during the non-activity period. My current workaround, therefore is:
press and hold GPS;
once through the lock-up press SET (to back out of the GPS fix);
then quickly press GPS again to select activity.
Initiate and control activity as normal after this.
All this is rather clunky, but gives a way to use the watch (sort of) normally.
a) Yes, assuming you have the downgrade package (for example from the last beta install version pakgae). And the rollback resets your device to factory settings, so the simple reset (without the rollback) seem to be less invasive than that.
b) yes, see the System Settings » Update options on the watch
