Two remarks

[Freddy]

3626313838540 wrote: … Let´s say that Jack starts by going down to this room before doing anything elsein the transit area.  He goes down to the room below and up again at the ladder furthest to the right.  Going that way back, he is forced to trigger a floorbutton that toggles gold to silver blocks.

My guess is that this should NOT matter.  Jack should still be able to use his rainbow key anywhere he pleases, wright?

I was well aware of that manoeuvre in room 17300 where Jack leaves the green door closed and kept his key. But I was afraid that there should be a spot where the blocks got toggled while having no key. It is supposed to be impossible and I do hope I am right. But with a key, no reason to go back into the purple area. Just use the rainbow key on any reachable coloured door.