If a 12 volt battery is rated at '14 amp hours', does that mean it is
capable of powering a load that draws 14 amps, at 12 volts, for one hour
before the voltage starts to sag below 12 volts? Or does it just mean that
if the battery was completely exhausted using a custom load that continued
to pull current out of it even as the voltage tapered off, and the total
power added up and restated in terms of 'amp-hours', it would be the
equivalent of 14, but the reality is that if you had a load that drew 14amps
at 12 volts, long before the hour was up, the voltage would drop below 12.

How long would a typical 14 'amp hour' gel-cell run a 12volt, 15amp load
before the voltage dropped 10%?

If you had a 12 volt gel-cell that was partially (say 1/3 )depleted, and you
simply hooked it straight up to a 12 volt ac/dc power supply, would it
recharge? What would happen when the battery was fully charged?