Greetings and Welcome to Just answer.
There is an actautor on the drivers side of the heater controls above the dash that controls the actual door positions. It has a couple of rods attached to it. See if that moves. If not then you likely need to replace it. See also if the rods have come loose.
This does not have any affect on the rear. The rear is likely an actuator to control the door.
The rear has its own systen in the right rear of the vehicle.
I do not have a clear diagram of the rear system. The actuators are behind there and are vacuum controlled.
For the front, what I mean is the actuator moves, but does it move all the way? I have my doubts so if you take the actuator off the heater box and move it by hand, you can tell if it is moving or geting stuck on something. I honestly think something has fallen down the vents and is causing the door not to move fully or the door is broken inside and causing this.
Yes, the same actuator in the rear changes from hot to cold. It is a door that this actuator moves.
The same goes for the front. The actuator, a single actautor changes from hot to cold, and a different actautor changes the mode from floor to vent to defrost.
Behind the glove box.