> the underworld has been described as having an edge in like, every game, or there is something that goes against it not being never-ending
The Underworld has never been described as having an edge - only the planet is, and the Underworld completely dwarfs the planet and stretches out beyond its borders in every game we can compare the two in.
I assume you're talking about the statement by Gaia on Chains of Olympus where she states Kratos fell next to the edge of Hades when he reaches the Underworld, correct? That statement is not saying the Underworld has an edge, as I have detailed in the past. The very next scene shows that Kratos is on the edge of Hades, which contains a waterfall of blood that leads directly to Tartarus, the infinite plane that directly surrounds and exists beneath Hades, the upper underworld, as seen in the next cutscene in the linked video. The term "Underworld" is used to collectively encompass everything within that area, including Tartarus (which are literally called the bowels/depths of the Underworld multiple times)
> Cronos creating time is solely a WoG thing (which isn't inherently bad or wrong but it kind of invents new stuff that was never really in the story)
Cronos creating time isn't just a WoG thing. Cronos has been implied to be some sort of time deity as far back as God of War II, and there is evidence on the new Norse games as well regarding him spawning time, as well as statements on the God of War 2 novel which suggest as much. The WoG pretty much confirms the implication.
> which is kind of weird when that would imply that matter has existed in a timeless void for a while
Time doesn't need to exist for space to exist. If you take this literally, even the existence of corporeal Gods who predate time would already imply that matter existed in a timeless void, since flesh is matter, so no need to overthink this particular aspect.
> As well, the statement suggesting that time began when the Cycle did doesn't necessarily mean he created time itself.
The cycle began with Cronos, killing Uranus. Therefore when the statement says that the Cycle began once the very construct of time began, is an implication that the existence of time is tied to Cronos in one way or another which is explicitly confirmed by WoG and implied by the novels, which state the Titans who are older than Cronos like Gaia are unbound by time, and there is explicit feats showing this, such as Gaia being omnipresent through time itself and knowing the events of the future and the past even when she is on her past form.