Is it possible to land, taxi, park on the apron and have everything in place (steps/buses) and open cabin door in 4 mins?
That depends on the where and when.
You're unlikely to get
all the above done in 4 mins but I know of at least one airport where, in the right circumstances, you can land ( The "ON" event) and be parked up (the "IN"event ) in less than 4 minutes so I guess getting a door as well is not completely out of the question...