WereCatf, many many thanks for answering my questions.
i know my questions may sound silly to you, but i am very keen to understand.

blueheadset support these hand-free profile, does it mean they can only access to the voice handling part of the phone? can iymbe set to for example, using the volume button to zoom in/out? or estabilsh a netweork connection by clicking the answering key? what is defining the functions of the headset? the firmware? how does the firmware/system programme intereact with the phone? is the phone sending all the commands? or the headset can command the phone as well? can the firmware be accessed by the phone via bluetooth?

again, many many thanks.