I suspect you may be misunderstanding time dilation. From the perspective of a particle, time always passes by at 1 second per second. If you yourself were to travel at relativistic speeds (relative to, say, Earth) your perspective of time wouldn't change at all. However, observers on Earth would see your "clock" to tick slower. That is, anything you do would progress more slowly from their perspective. In the very early Universe, a given particle would see most other particles moving at relativistic speeds, and so would see their "clocks" tick slower. These sorts of relativistic effects would influence interactions between particles during collisions, decay rates, etc, but are all things we know how to take into account in our models of the early Universe.

I think these are all excellent questions, but to my limited knowledge they haven't been answered yet. I think these are all active areas of research in cosmology.

They are fun to wonder about though. If you have a deep interest maybe check out your library or bookstore. Once in a while scientists in these fields will write a book about their work in these areas.

The way I understand it, (which is virtually not at all really!) there is no overall universal time or background clock like a force field of time or "stable rhythm" that everything experiences. But every observer experiences its own time, relative to whatever point of reference is used.

This is where my meager brain fully melts down.....

If everything is moving through spacetime, the faster through space, relative to C, the slower you travel through time, the slower through space, the faster through time.

So if every particle is moving away from each other equally at C, from each ones perspective it's own time is slowed to 0, so now everything is eternally rushing away from everything else with no time passing.

Now my reasoning and vocabulary fail completely tbh,