"a few millimeters in diameter" is finite.
You say the diameter is now infinite.
An expansion of infinite distance in 13.8 billion years requires what average rate of expansion?
"A" x 13.8 billion = Infinite
There is no quantity "A" that can complete the equation, i.e., there is no rate of expansion that can reach infinite distance in 13.8 billion years, or in any finite time period.
Furthermore, the finite "few millimeters" cannot reach infinity at any speed over any amount of time.
Further still, at any finite speed of expansion, over any finite time period, the expansion would be NO CLOSER to infinite in distance than when it started at "a few millimeters".
Any expansion of the finite diameter would be the next finite diameter.
For it to reach infinity is impossible.
An infinite distance is unreachable, in any context of physical reality.
Hence, the principle of infinity - "that which is unreachable"
And none of this depends on whether or not it can be measured, or whether it is observable.
It's impossible either way.
What was a few millimeters in diameter was essentially infinite in content.I showed you where the theory states a singular point became the entire observable universe.
But in the expansion a singular point also became infinite points to expand from.
It didn't take an intelligent design, we cant find a creator , we cant find an edge , it only has a time like horizon, but none of any of your beliefs of divinity or finite qualities, are anywhere to be found.