Thanks all for your support. Based on your input and rechecking the lesson material my new understanding is...

These 1, 2 and 3 point perspective systems do not exist. (https://drawabox.com/lesson/1/6/123pointperspective)

So I don't care (at least for now) in what perspective the whole Scene is, in the end it's 3D and every object has 3 PVs. VPs could be in infinity, but they are always there. If I want to move or rotate a box in space I can describe that by doing relative manipulation of some VPs.

The "rotated boxes", which are tapered boxes no classic box with 90 degrees like in the 250 box challenge, have all 3 VPs. For the first box one VP is in the center the other two are in infinity. Rotation can be described as moving VPs.

Boxes in 250 box challenge are not rotated as long as I see them as independent boxes. A single box can never be rotated. The viewer looks at the single box from different angel. I can control with 3rd vanishing point the viewing angle of my eye/camera. In contradiction Rotation is always relative from one object to another. So if I want to see the boxes, which I draw on the same page in relation to each other they are rotated, moved, scaled or whatever relative to each other.

Thanks all for your contribution to my new understanding. If you want to correct or add something feel free to do so. I see my understanding as a working hypothesis, which is good enough for now and will be improved with every new input.

Best,

Neuromancer