...... so now I know absolutely nothing...
Yes, that happens to be the only accurate thing in your last post.
I hate to disappoint you, but you aren't exactly well-versed in the laws of space; rather, you seem to be operating more on mere intuition, wouldn't you agree?
I suppose your efforts are commendable, given that we are discussing philosophy here, but I have already noted on science for science that science is increasingly encroaching upon the territory once held by philosophy. As these subjects begin to undergo rigorous scientific study, we arrive at conclusions that are far more precise, convincing, and—crucially—verifiable than any purely philosophical insight could offer.
But, returning to the matter at hand:
According to the explanation of space, there are four levels of primitive/fundamental entities existing within three spatial dimensions:
1. A Point — a position defined by coordinates; a zero-dimensional entity (zero dimensions required for description)
2. Length — a set of points arranged linearly; a one-dimensional entity (one dimension required for description—length)
3. A Plane — a set of points arranged in all directions within a flat surface; a two-dimensional entity (two dimensions required for description—length and width)
4. A Body/Curved Surface — a set of points distributed in all directions through space; a three-dimensional entity (three dimensions required for description—length, width, and height)
If we incorporate the temporal component, we arrive at a fifth entity:
5. An Event — a point possessing a position not just in space, but also in time; a spacetime entity (one temporal dimension included)
Beyond this, one can make further assumptions, similar to the initial entities but with the addition of time, though those descriptions become significantly more complex due to the inclusion of motion and transformations.
Therefore, your point within the cross-section of a cube is not some three-dimensional body possessing its own "invisible" dimensions; it is merely a point with its specific coordinates. The cross-section itself is simply a surface, yet all of this exists within the context of the three-dimensional body of the cube. Please, do not conflate coordinates with the dimensions that certain concepts occupy in space.
It is true what you say: in practical application, every spatial point is simultaneously a temporal one, but that is not necessarily the case when we are looking at a mathematical mental model.