The rear brakes are operated by the foot pedal, just less than the front. There may be less cooling of the rear brakes so they may still get quite hot.
If the rear brakes are a similar temperature, they are probably working OK.
I think that you have a failed wheel bearing, and the wheel is twisting a bit, with the top moving to the inside as you corner. When you apply the handbrake, the brake pads hold the wheel in the right place so the noise goes. Also the rotational force on the brake pads has to be opposed by an opposite force on the bearing. This change of force may cause the bearing to be quiet for a minute or two.
My experience of main dealers is that bearings are not diagnosed properly:- http://www.malin.me.uk/audi/bearing.htm