There is no "ALL", there is always more.
Scholars are quick to point out that infinity doesn't exist. They are absolutely correct, but that doesn't mean the Universe is finite.
Infinity is the non-existence of a limit. If a non-existence existed it wouldn't be a non-existence. There is a finite distance between every two points in the Universe, but there is no point, however distant, where it ends. Some mistakenly believe if there is a finite distance between every pair of points then the farthest point in the cosmos must be a finite distance away. The act of defining two points immediately sways the realm of consideration from the infinite back to the finite. When dealing with infinity, there is no limit, there is no 'farthest' and there is no 'all', there is always more.
A finite cosmos would contain a finite amount of 'stuff' - space/mass/energy. All of those elements would be quantifiable into measureable volumes with defined physical domains. By summing their volumes and delineating their configurations one would be able to determine the boundaries where some mythical 'cosmic wall' should exist. The fact that no wall and no defined point of infinity exists serves only to further validate the concept.
Given any point of origin, three independent XYZ coordinates can specify the relative position of every other point in the Universe, so the cosmos is said to be 'three dimensional'. More accurately, each point can be considered the hub of three axes from which an unlimited number of unique vectors can be derived. I consider those vectors, not the three axes, to be 'dimensions' and they are infinitely various. If the Universe were finite, then either there must exist some pair of points within a finite distance at which travel in any direction will not increase the distance between the two or there must be a finite XYZ coordinate that falls outside the Universe (i.e.does NOT exist). There is no data or precept of logic that endorses either case.
The old 'balloon ploy' is often put forth as a three-dimensional example of cosmic expansion in a four-dimensional hyperverse. So long as the balloon is expanding faster than anything can traverse it, a subject can travel forever without hitting a boundary. Stroking the ego of the unwary layman for his ability to understand a hypothetical abstraction, pundits propose this as an example of a Universe that is finite but unbounded. But it doesn't hold water. At any given instant there DOES exist a point on the balloon at which motion in any given direction will not increase the distance between the two. It is, indeed, a limit - a boundary to the ability to increase distance.
If someone wants me to believe the universe is finite, then all they have to do is simply convince me that for some given instant the value of at least one of the XYZ coordinates has or had a limit. And if anyone wishes me to believe there are more than three dimensions, then show that there are locations in the cosmos which cannot be specified within those coordinates.
Saying infinity expands is trying to apply a relative term (infinity expands relative to WHAT?) to a non relative situation. To expand is to increase the value of some limit and only that which has a LIMIT can expand. The Universe is everything that exists, not just the KNOWN universe. Multiverse is a sleight of hand bit of esoterica used by Big Bangers to obfuscate the weakness of their argument. There is only one Universe and it encompasses everything that exists.
The scholarly term 'finite but unbounded' is self-contradictory. Finite explicitly means a limit and either that limit exists or it does not. There is no limit that is somehow unlimited due to some exotic configuration or mystical process. If a limit exists, you can point to it. It must have a specific location relative to you.
"Beware and sail ye not too far into space lest
thou fallest from the edge."