The set was really evaluated as brand new condition although it was listed as C rank condition, the seller might be using a professional 3rd party supplier to supply its auctions so the store might be unaware of the actual condition of stock. If the motor is shiny and clean with the battery terminal facing downwards, it could mean that it was untested. If another monorail set was obtained, I think it might be possible to go all the way from monorail station, to airport, back to monorail station.
I think it was a coincidence that the piers are compatible since there was a 4 or 5 year gap before the release of the yellow piers.
Monorail car does not use batteries, it uses weights and moves down the line. So it relies on gravity and weight.
Building is only single direction, and the lever will move backwards without affecting monorail position just to let the train pass through.
Yellow trip arm, the monorail slope rail? That is to allow the monorail to climb to a higher level.
