But still we encounter another problem:

It seems to be a proven fact that there is no “end” of the universe. But in the example of the previous paragraph, the “sand people” would find easily the four sides of the photo and in fact the endings of their world.

So the “paper” square form seems to be the wrong one.

Assuming that there are no unknown primitives in the 4 dimension , which are projectable in our universe with the same result, there is only one form for our model that provides all necessary conditions to our “sand world”