If you unchange X, it will remain X ad eternum. But if X changed, you must conclude by deduction or observation that something caused it to change. That's the principle of causality. The absence of a cause is an impossibility in physics.
*sigh*.... Again, you are taking what we see in this spacetime with out physical laws and trying to apply it to a scenario that is completely different because "common sense". You cannot extrapolate what pre-BigBang conditions were based on post-BigBang conditions. What you describe IS A primciple of physics....in OUR spacetime with ITS specific properties. You cannot extrapolate that an environment outside of our spacetime.
Therefore, the gravitational conditions that determined the emergence of the universe necessarily had an a priori cause, and there was a time interval between the two.
You are now presuming gravity in the pre-BigBang conditions! Remember, these are the rules INSIDE of OUR expanding spacetime. We can't tell what is outside of our existing spacetime, what the conditions are, the physical rules.
For instance, did you know there is a concept called imaginary time? Mathmatically, it's very usefule in quantum mechanics, it may help explain pre-Big Bang conditions, it's completely alien to "common sense" and it's unproven.
My point is is, you CANNOT rely on your experience in this spacetime to make extrapolations about what came before it. It's unobservable.
Therefore, time precedes the beginning of the universe. Infinity does exist. We just cannot comprehend it. And that's ok.
You can assert that, but you have not provided any proof, either logical, mathematical or physical.