Electronically, through the settings in the touchscreen panel on the dash. These are not child locks, but rather set the behavior of the door latch when the door is locked.

Does it have a fail-safe configuration if electricity is lost like in the examples above? If not, the ability to change configuration may not actually mitigate the failure mode

Yes, there is a manual door lock button-thing on the door next to the door latch. Though honestly I don't know if that works when the power is dead. As cars move to "fly by wire" this becomes a larger concern - less mechanical linkages, more buttons/switches + wires.

For example to open the back you push a button on tailgate and then pull to open. That button is definitely not a mechanical latch, so if the battery is dead then you're not opening the tailgate.

This would be an interesting experience - go to an auto dealer and ask them to disconnect the battery, then see what still functions.