How can you, or anyone, possibly know that?
I don't have any particular preexisting background in mind. Just a preexisting medium of unknown structure, and that this is a possibility that can't be ruled out. Anyway, I don't have in mind any sort of classically contracting spacetime.
It's obviously not relevant to t > Planck. We're talking about t < Planck and the possibility of a finite disturbance as the beginning of our universe -- which is inherently speculative, and therefore a possibiltiy.
Homogeneity doesn't preclude a center or edges if the homogeneous volume/medium is finite/bounded.
I don't know what you're referring to by this.
Nor do they necessarily exclude it, even if they might obviate it.
This is nonsensical. If it's finite, then, by definition, it has a spatial edge or boundary and a center. We just have no way, at least currently, of reasonably inferring that it's either finite or infinite.
Higher dimensional topologies are, afaik, employed for calculational purposes only, and should not be taken as literal descriptions of our universe.
Ok, but this doesn't rule out the possibility of a preexisting medium/space, ie., the possibility that our universe is part of something quite larger, perhaps infinite.