Several questions regarding the nature of the universe

[Rysiu]

I have a few questions about the nature of the universe. I'll start with the first question:

What was the size of the universe in Photon epoch? (in meters or light years)

How can it be calculated? On the Internet, unfortunately I did not find accurate data.

Sorry for my english - it is not good

 

[Chronos]

We can calculate the age of the universe at any given epoch, but, the dimensions of the universe is more complicated. For example, we know the age of the universe was a little under 400,000 years when the CMB was emitted, but, not the diameter of the surface of last scattering. You would need to know the entire expansion history of the universe for that, which is unknown.

 

[Rysiu]

Ok, thx.

Another question: We can estimate what was the pressure in the Photon epoch?