I have to guess about your Mechanical competence on this given your questions ..

Its not hard , but I started working on my own Bikes when JFK was still breathing.



Change which gear the 2 on the outside or the 3 inside the Hub?


no they are not sudden like a light switch , you are making an unrealistic demand ..

maybe you will like a High end Di2 race bike drivetrain better?


What side of the Atlantic are You?

maybe you can go back to the Dealer and say "make it So"