Of course. I agree that unfortunately, there's no way to know yet if there is some kind of container or boundary at the edge of the universe.
But, Is it possible to Mark the location of the inner-core-point of this universe ?
No.
Consider the idea of the "observable universe". This is a spherical bubble with a radius of 13.7 billion lightyears. That is to say, you can "see" (assuming the proper equipment, like hubble space telescope and alike) objects upto 13.7 billion lightyears away in all directions. There, you hit the horizon. You can't see beyond that, because the light from beyond that horizon hasn't reached us.
The observer, meaning you / the telescope, stands at the center of the observable bubble.
If you move to another galaxy, this bubble will move also. At all times, you remain at the center of that observable bubble.
The universe however, is far far bigger then a space-bubble with a radius of 13.7 billion lightyears.
See, space expands at a much faster rate then the speed of light.
People tend to think that that can't be the case, because "nothing can travel faster then light". The thing is though, nothing (with mass) is
travelling through space. Instead, it is space itself that expands. This expansion has no such limitations.
So even if you would try to move to the "edge" of the universe, even assuming you can travel at the speed of light, you'ld never reach it, since that edge moves away from you faster then speed of light.
So because of this, it is impossible to pinpoint "the center" of the universe. In reality, every observer always stands at the center of his/her/its spherical bubble of the observable universe.
To illustrate with an analogy.... Suppose you find yourself on a boat in the middle of a vast, vast ocean. For the sake of example, we'll assume you have no maps and zero reference points to pinpoint your exact location. In your 360° line of view, all you see is water stretching from where you stand, all the way upto the horizon. Once again, you are at the center of your "observable bubble" - with no way to pinpoint the "center" of the ocean. Simply because you have no reference points.
Moving to another place, it will look the exact same. You have your observable bubble and you can only see as far as the horizon allows you. And all that, without any reference points of where the coast is.