Where does it ends?

You may find this very crazy, but when I started thinking about it, it really blew my head out.

We are living in a world of "midways". In every dimension we are at just "some" position. We have no idea about the two extremes of the dimension. Be it space or time. In either of the two dimensions, we are just stuck at midway without knowing the starting and ending points. As per my understanding we are not even sure that such extemes exist or not. Terming something boundless does'n fit in our current understanding of the world, since we havn't seen anything boundless. Every object has some starting and ending point, both in space and time. With repect to space, it means every object has finite dimension. And with respect to time, it indicates finite existence period. This is applicable to all objects around us.
So where does this space ends? Universe is the name given to space extending all around us. There is nothing beyond this universe. Here if the word "universe" is treated as any other object, then the question arises, how come it is infinite, boundless when all other objects are finite. Why are we giving universe an infinite space. Why can't there exist any other realm beyond this universe, which itself encompasses this universe?
With our current understanding, we can organise all objects in this universe into spheres of different scope, with every sphere enclosed by an outer sphere and universe forming the outermost one. Our earth forms one such sphere, consisting of continents and oceans each forming a sphere. Sphere represented by earth is itself present in the sphere formed by solar system, which has more earth like spheres in the form of other celestial bodies. Same can be extended to form hierarchy of solar system present in milky way which is in turn present in universe. Another way of organising objects in universe is in a tree structure. Every object is a node of the tree. Earth and similar celestial bodies are present at same level. Similarly galaxies form another level, one level above celestial bodies like planets, stars etc. Node representing an object is parent of all nodes representing objects which come directly under former object. Just like node represented by Milkyway is parent of every other node which corresponds to objects present in Milkyway. Thus Earth node is a child of Milkyway node. At the top of the tree, the root node, is the universe, parent of all other objects.
Now, my point is that why do we stop at universe? Why can't this hierarcy or tree be extended beyond it? Simple logic says that universe must also be a part of something above it, just like every thing else is. Why is universe considered ultimate or topmost sphere. It is like saying something called X is not present in anything else. How is this possible? Such an idea defies the property of every object found in this universe which is, that every object is part of some other larger object. Why and how is this property not applicable to object called universe?
Another thing to point out is that we acknowledge that universe is expanding. If it is the topmost sphere, enclosing every other object, then where is it expanding? Blowing a balloon makes it to expand in the space outside its surface, that is it occupies some more space in the object enclosing it. Applying same to expanding universe, it follows that there is space outside this universe and that there is another entity enclosing this universe, which is providing it space to expand.
If you buy this logic, then it automatically gives space for another question.

If universe is not at top of tree, then where and how does this tree ends?
If we continue by above logic, it looks like there couldn't be any end to the hierarchy since every object needs to be present in something bigger and larger than itself. But it has to end somewhere. That means there is something which is not present in anything else, which is at top of the hierarchy tree, which is the ultimate sphere, encompassing every other sphere in itself.
These two concepts look like contradicting each other:
1) Hierarchy of spheres or the tree should end at some point.
2) Everything is a part of some biggert thing.
Each of them sounds logical but cannot hold true without violating the other one. If every object is present in some other bigger object, then how can this organisation of objects ever end? And if there is anything which is encompassing all objects then how is it even existing? It is hard to imagine an object which is not enclosed in another object. Our current experience forbids us to believe this. But again, this hierarchy can't extend ad infinitum. It needs to end somewhere.
Does that mean we are missing something in this whole setup? Is there any glitch in the foundation of this argument?

Now all above arguments hold true when we treat universe as any other object, which is the case when we say "galaxies are part of the universe". Essentially, here universe is just another entity like galaxy and is supposedly at one level higher than the galaxy.
But "universe" can also be treatd in another sense. A boundless universe is in essence acting as synonym for the dimension space. Now treating universe as object is similar to treating a dimension as an object and trying to find its boundary is like finding dimensions of space, which doesn't really makes sense. A notion, an idea, a concept can not be expressed using itself. So, trying to find bounds of universe is like calculating limits of space. Space is just a dimension, not an object. A dimension is just a concept, an idea which has no physical existence but used to describe objects having physical existence. Again treating universe in same sense as dimension space, it becomes difficult to digest the phenomenon of expansion of universe. How can space extend? Space is already boundless. It is a concept, not having any physical existence. It is like extending number line beyond infinities. Expanding universe makes sense only when we treat universe as object.
So, does that mean we are living in a boundless world, which keeps extending, no matter how far we go. It is similar to tracing infinity on a number line. No matter how large a number you write, you are still at same distance from infinity. As soon as this concept of infinity comes into picture, all our established principles take a nosedive, hitting face down on hard floor.

My belief is that if we ignore the phenomenon of "expansion of universe", then universe should be treated in the sense as dimension space, a notion that describes the characteristics of the physical objects. Universe itself is not an object, b'coz had it been so, it would be bounded, finite, thus giving rise to above mentioned questions. In such scenario, the idea of an ultimate sphere or a root of hierarchy tree does not hold true since there always exists a possibility of another object that is larger than the current root or ultimate sphere. With respect to number line concept, it is like treating 9999999999 as the largest number encompassing all others, but you can still find another number which is larger than 9999999999. Moreover you can go on doing this, it is never going to end. An object as large as infinity cannot exist, b'coz that would make it boundless. A boundless object can exist as a notion only, just like dimension space. In fact, a boundless object can be used in same sense as the dimension space, and that is exactly the case with word "universe" as well.
But, since the observation of universe expansion been corroborated by several sources, then, considering it as a fact, universe should be treated as another object in this notion of space as argued above. Which means we are still not aware what lies beyond this universe. It is like we are living in a balloon which is being expanded by blowing in air. Our universe is this very balloon, and we still need to explore the realms outside this universe. This doesn't really makes universe infinite or boundless.

This piece of writing took a hell lot of thinking from my side and really found it difficult to convert thoughts to words, more so in a way that can be easily understood. I am still not entirely convinced if I have been able to convey what I wanted to.