How can i receive the hardware key button event On

How can i receive the hardware key button event On Windows phone 8 App?

I have many problem,
The WP 8 is available features are very limited. The Windows CE / WM is a very different behavior.

I want to access the OS Layer by the API (Function)

Back button : Success. I found this key event.
Home button : ??? (I don't know)
Search button : ??? (I don't know)
Volume Up / Down : Just working volume.
Camera Key : Can i change the default camera app?

http://msdn.microsoft.com/en-us/library/windowsphone/develop/hh202963(v=vs.105).aspx
Power Key : Can i optionally lock the power key?
OEM Key (Barcode Key) : Push the button, I want to execute the My App?

[Additional]

Sorry. My Project information was too little provided. I developed the WP8 App in the WP Device OEM Manufacturers. So I can access to "OS, Device Driver, App". But there are various MS documents, By First Time, The developement is too hard.

Have you ever used these methods can I? - Named Event - SendMessage / PostMessage - Other Communication

I guess the Key-Point "How can i communicate Device driver <-> App"

I am studying now the following Function. - Service Agent - IPC

You cannot access the majority of those buttons, by design. By not allowing applications access, it means the end user has a consistent experience with the standard platform.

You can create a new "lens" to act as a replacement for the default camera application.

That's not to say though as an OEM, that Microsoft would not provide additional access that is not available to a standard "Store" application. That type of access is often protected by a non-disclosure statement however.