This was a fun list of 10 here "3. Plasma-filled cosmos", briefly discusses inflation. In December 2013, Alan Guth published that at the moment of inflation, 10^-36 second after BB event, the scale map for the universe was 10^-53 meter to 1 meter today. That is some expansion here The Universe expands by some 10^53 order of magnitude or more. Using the cosmology calculators, when the CMBR formed at recombination, the Universe diameter about 80 to 82 million light years across compared to the present size, said to be about 93 billion light years in diameter.
Why is the finite universe shaped like a donut? So it can take a dip in the Milky Way. The "theory" that the universe is a self contained three D substance is hard for me to swallow. The fact that, according to this theory, one could go to the edge and loop back to where you began. Many have stated that nada exists outside our known universe. We are the only universe in existence, and don't you forget it. Containing something with nothing is a hard thing to hold up. Hold on. I will create an infinite field of nothingness that would contain the vastness of the universe. I will create nothing out of nada. We laugh at people who believe that the world is flat, but we believe the universe is the only thing in existence. As far as the inflation theory, maybe this universe is the result of the merger of smaller universes, similar to that of the merger of galaxies. What will happen after the Milky Way and the Andromeda galaxies merge, would those born in this galaxy know how it came to be. Do we know how the Milky Way came to be? The Milky Way came to be by the mergers of other galaxies, do we know when and how these mergers occurred? No. Do we know how this universe came to be? Not really.