The absolute center of the universe is any selected frame of reference.

The 2-D analogy unnecessarily criticized in another response to your post is not half bad, so long as we remember that the universe has more "surfaces" than that. Frames of reference are invariant, and based on Photons in the SRT/GR concept. As we look outward in the universe from any frame, we see the Astronomical, macroscopic antipode, the "Big Bang".

As we look inward, at 10 to the minus 33cm we reach the singularity at the submicroscopic antipode of the universe, which like the macroscopic antipode is everywhere in cosmic reality. We cannot see our other half, in the dual universe because we cannot see over the horizon- through macroscopic or microscopic singularity, and the time separation is vast.

A four dimensional projection would be looking at a ball. We cannot see "around" to the back side. (Is is possible to "rig" a mirror in the universe?!)

There is no "center" in the universe, except as each entity observes it. The role of those "entities" in creating, conserving and sustaining the existence of the cosmos is a potentially fascinating area of investigation!

Best Wishes! Sam Cox