Welcome!
The beta patch is very easy to install (just unpack to a proper folder) and it will go to Steam relatively soon too to be installed automatically.
For multiplayer check out this thread
http://forum.1cpublishing.eu/showthread.php?t=35030
or videos
http://forum.1cpublishing.eu/showthread.php?t=29379
List of aircraft is rather big and should be in official game description. Amazon sells Steam copies only as well as all other retailers. Look for special sale deals.
PS. Not sure about native mouse support but you can use 3rd party joystick emulator software.