Questions about gear oil change hand switch

Hello
the quattro transmission has 2 screws (once the filling and a lower drain screw) at the front of the front axle differential at the drive shaft and then still at the rear of the gate endifferential an outlet screw (must also be magnetic) Is the gate and the front axle differential connected, so that I only have to fill oil at the front of the drive shaft? I found out that there's a screw at the top of the gate...

Mfg