I drove 1800 miles in a Hydrogen Car

#1: If this is H2, why does it want to combine with oxygen so bad? Shouldn't it be happy just being H2? 

#2: BEV's have their main batteries but they also usually have a regular car battery for running the low power stuff (dome light, alarms, etc.). Is there a battery or 2 in FCEV's? Or maybe a super-capacitor? 

#3: (Somewhat related) Is there regenerative braking in a FCEV?