can you turn the illuminated entry on and off

Sure, open the door and it lights up. Close the door and it goes off.

my datsun and my toyota had off-door-on a three position switch. Is this not the manual switch you see on the light?

Not sure specifically about the Impreza, but seems like a majority of cars have the 3 position switch: One that corresponds to the Door (lights up when door opens and then dims to off after closing door), 2nd position will keep them ON all of the time, 3rd position will keep them OFF all of the time ...I'm assuming you mean the map/entry lights in the vicinity of the rear view mirror??