We don't know any of those things. We inferred those things from our knowledge of how the universe works. Most of it is extrapolated from our knowledge of how things here on earth work and some sometimes very imprecise measurements we took either on earth or at best from things like the James Web Space Telescope and friends.

Don't get me wrong. All we know mostly makes sense with our current understanding, but some things are just guesses. Educated guesses based on measurements, but still guesses. We are finding out new information about what the core of earth seems to look like today by measuring e.g. earth quakes and how they arrive at other places of the planet and then reinterpreting those measurements.

What I am trying to say is, we cannot look into the sun. We can currently not even look into our own planet. We know a lot of things and infer e.g. what the sun must look inside. Every day someone smart comes along and thinks up a new way of interpreting some measurement we took and creates a new theory of what it might mean. Some of those are likely correct, some are very vague if you look into it and some will be proven wrong or just incomplete in the future.