sound at tranny when operating brake pedal
 

Is it normal?

Whe I press or release breake pedal, I hear some sound from trasmission handle area.
There is no sound from there while the pedal is in steady state.

check your flex discs.

Flex discs were replaced in June. I ran, usually gently, about 4000 miles with new flex discs. Can they wear so quickly?

The noise can be heard even when the car is at rest: transmission at P, parking brake engaged, and then press & release brake pedal. I hear some clicking kind of sound when I press brake pedal, and when I release brake pedal.

Sounds like you're describing the shift lock. You need to have you're foot on the brake to enable you to get the shifter out of "park". You'll get an audible click when you press the brake pedal.

I also hear the click when I operate brake pedal while the car is going with the gear at D. Is it usual with the shift lock?