A) HSN aka High speed neddle
B) LSN aka Low speed needle

C) Throttle stop screw , this sets the air gap so the it doesn't get completely cut off when you apply brakes, it should be set .5mm minimum to 1mm max open while holding full brakes,(they say 2mm,but that sounds like alot to me) take the air filter off and get it adjusted before you do anything else, Do not adjust it while holding the brake on!! you can damage the screw and or the barrel

D) Leave it alone,, should be set flush,,Some people call it the midrange needle but it's really just sets the splash bar position,,leave it flush with the brass case,, If you move it you'll have to move the LSN also

Good luck