What do you mean for "the rest"? There are a series of stations you can access, and what is not alread available simply does not exist, f.e. Maschinenraum, bow quarters, torpedo rooms, toilett

and so on.
In SH3 you have AFAIK
-Bridge
-Conning Tower
-Control Room (Aft-Forward)
-Radio
-Sonar
.Captains Bed
Aside of that you can man gun, flak gun, both scopes, and see in 2D crew management, weapons management, radio messages, charts & attack map
There are no other rooms/stations, but there is nice mod called "Open Hatch" which allows the hatch of the control room to be open and see from the control room the radio and sonar operators and vice-versa.
Some correct me if I'm wrong:hmm: