Gen 2 jump start question:

Yes, you can jump there. Just like you can swap the discharged battery for a new battery and the car will start again (if the battery is the only problem.)

I would be careful though that bare metal on the positive clamp on the jumper cable is nowhere near any bare metal on the chassis, that it is firmly attached, and the negative cable should not be attached when the positive is placed. Lots of sheet metal, bare bolts, and I think even some bare metal nearby. It would be bad if the positive cable popped off and hit any of that while the negative cable was attached. Find a nice big bolt elsewhere in the trunk (NOT the normal battery ground bolt) to attach the ground clamp on that cable. I wouldn't go straight onto the negative post, just in case something goes dreadfully wrong with the battery in the car when power hits it. You really don't want to be leaning over a battery if that happens. (Do AGMs ever blow up, maybe that is just a flooded lead acid battery problem?) The problem with the normal ground bolt is that it is tucked back in an awkward place posterior to the battery, and it seems fairly likely to me that a cable clamped to it might pop off.

 

Yes, no problem... Main issue with Prius is if you get polarity reversed you damage the car.

 

just jump stared mine on the battery at the back with one of those small boosters with the capacitors in.
The only difficulty was that I couldn't open the hatch because of the flat battery so had to crawl inside and release the catch by hand.
That's a pain in the arse when you are my age.

 

Was the booster in the trunk? You couldn't jump it from under the hood?

 

if you put 12 volts to the jump point under the hood, the hatch will open