Asterisk PBX Phone system

I need an asterisk pbx ( on a standalone device) that would function in the following manner: 1) call comes in and PBX examines the CID 2) If CID is in contact database, it will announce to caller to please hold on and then PBX will announce over intercom system the callers CID 2a) if extension is picked up then call is completed 2b) if extension is not picked up then call is sent to voicemail 3) if CID is not in contact database then the pbx will ask the caller for his name and which extension he wishes to reach. 4) The pbx will then announce over the intercom the caller and extension he is trying to reach 4a) if extension is picked up then call is completed 4b) if extension is not picked up then call is sent to voicemail there are some other minor points , but this is the main portion of the project other details would be a 1) choice to have a directory of all extensions 2) send voicemail messages left by email to extension owner and all other usual features of a pbx and voicemail system.