"Most things mentioned here are sourced from various authors and materials such as Wikipedia. Nothing are mine, only the extremely twisted idea..."
We are only limited by our imaginations, so here are bits of mine (again in the context of above):
Universe:Space and Time, Rules of Physics
Multiverse:Parallel Universes, i.e. different flavors of space and time, different rules of physics,
Metaverse:Includes "other" dimensions, i.e. spiritual (rules of physics, space and time are irrelevant), pocket dimensions
Xenoverse:Includes planes of existence including but not limited to what is defined as a "dimension", i.e. the after-life, spiritual hell
The Outside:"The void of the voids", "The space between spaces", "One-way exit", "It is what it is", said to be the gap the sits between Universes, Multiverses, Metaverses and Xenoverses. Part of the Omniverse.
Super/HyperUniverses:Higher/lower superdimensions. Runs "vertically" across Universe, Multiverse, and Metaverse but excluding the Outside.
Omniverse:End of Infinity, Infinite dimensions, HyperUniverses, "All that there is and there is not", "the heaven of heavens"
Physical beings like Galactus and the Celestials can only exist at the
Conceptual abstract beings perceived by human soul such as Death and Eternity can exist at the
HyperUniverses are like "levels" in the Omniverse (as a building with infinite floors) while a Xenoverse (and the lower heirarchies) is "a section" in Omniverse (again as a building with infinite number of sections). Therefore, each level of Hyper Universe has infinite number of Xenoverses while each Xenoverse has infinite levels of Hyper Universes. Beings like Yog-Sothoth, Azathoth, Fulcrum and TOAA operates are the Trans-Super Universal/Trans-Xenoversal or partial-Omniversal (there is no absolute as you will find out) level where they reside in a particular "level" of an infinite vertical hierarchy of universes and dimensions. This means they can move from one Hyper Universe and/or Xenoverse to another.
There are infinite number of beings that are more powerful (some are infinitely more powerful) than the four entities mentioned in the higher Hyper Universes. Moving on to the next higher HyperUniverse would greatly diminish a power of a being doing so. As it moves upwards to the next level, it's power diminishes further up to point where that being is simply annihilated/dissolved by the energies of that higher Hyper Universe. E.g. if TOAA is to move 3 levels above his current HyperUniverse, his power level will become like that of a normal human being. If he moves up further (level 4), he will be unstable and will slowly disintegrate. At level 5, he will perish instantly. This also holds true the other way around, e.g. a low power level being such as a human being is brought downwards on the lower HyperUniverse (granted that a human being has the technology to do this), that human being becomes powerful and can even become as powerful as the TOAA way down further.... to a point where the human being simply cannot go down further because his power level can no longer be accommodated by the next lower HyperUniverse. Therefore, there are infinite number of beings in the infinite number of higher HyperUniverses that simply cannot go down at TOAA's HyperUniverse due to their immense powers which cannot be accommodated. Imagine that...
Lastly, there is no entity or being that can reside everywhere in the Omniverse. Although beings from all HyperUniverses can "exit" to The Outside, it's a one-way trip and there is