It does drive backwards electrically as it has no gearing for reverse (IIRC) but when the battery is low(ish) the engine will run to power the generator.
Motor and generator are actually combined functions of the motors in the HSD gearbox, so this is a simplification
Have your parents use it every month for at least an hour (total running per month); if not for the traction pack, then for the 12V battery.
It won't start when the 12 is flat either.
It does seem a bit expensive for the years and miles, but if it has enough fairy dust on it all is fine.
51 mpg at over 70 mph is neat. But go see what it can do at 55 mph.
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gigameter or 0.13 Megamile.
For confirmation go to people just like you.
For education go to people unlike yourself.