how to move face along an axis without affecting other faces? I'm learning Blender and i face this issue that i can't figure out:

I have this isometric shape:


I was trying to move this face on red x-axis:


And this what happened, actually this is what i want to do , it's kind of a mix between extrude and move:


But when i tried to do the same thing to the left side, this is what happened, it's moving all the connected faces as well:


I noticed that if i merge all vertices by distance i cant move the face as i wanted anymore.

This is how the face looks when moving it before i merged the vertices "what i want".


Is there any way around this, or a un-merge vertices option!

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Edit :

This is what i'm trying to do, if you have good method to model it:



This way still has some issues , I know I can fill missing edges but later on I might be missing lot of faces :
Each edge is defined by 2 vertices, and each face is defined by at least 3 vertices. On the screenshot below, moving selected face is moving 4 vertices it is defined by. Since this face shares 1 vertex with the edge marked as (1) and 1 vertex with the edge marked as (2), moving this face, will warp those edges, because you will move half of the vertices defined by them:

You can see which edges a vertex is a part of, by selecting it, and looking for gradient lines:

If, while having the same face selected as on pic. 1, you right-click and choose Split, then the vertices of the selection will be duplicated, without any connections to vertices outside of the selection. Selecting a vertex again should make the difference obvious:

Selecting all duplicates (or just everything), pressing M, B, will merge the vertices, by removing all but one vertex at each spot and moving all links of those vertices to that one.
However, you probably never used Split. What you did use was Extrude, which takes a face A and duplicates it to face B, but also (unlike Split) for each vertex of face B it creates a link to the original vertex it duplicated in face A (as well as it creates faces between edges created this way). Then the new face is being moved along its normal. And what you probably did was Extrude, but then right-click, leaving the new face in the same spot as the old one, but no longer directly connected to edges (1) and (2) on the first picture. This is why you could move that face without warping those edges, and this is why so many people advised to simply extrude the other face - if you want to keep the consistency with the other face, but it is not the correct way to build &quot;proper&quot; topology.
Moving the original face:

Extruding the original face:

Extruding the original face, but right-clicking to leave it at original coordinates; deselecting it, selecting it and then moving it: