Another advantage for a dual motor / AWD setup. If battery is too olod or too full, the second motor could use up the regen energy for 'braking'. Would create a much more consistent regen behaviour.
This isn't really possible. You would be destroying energy. You have to dissipate the kinetic energy of the car into heat, or electrical/chemical energy in the battery.
When an AC induction motor is moving forward you can't 'power' it the opposite direction. When you go reverse to drive you can notice a quick 'jostle' where the car has applied the e-brake and the car starts moving the opposite direction.