Question: Why is the inner core of the earth solid if it is the hottest layer?

Hi Maestro, great name and great question!
I am not a geologist, but I can try to answer from some simple physical considerations.
In fact, it is really hot down there, but the pressure is also so high that the melting point of iron, that is the main constituent of the core, also increases. if the inner core is solid, this means that the pressure effect is so strong that the temperature is simply not high enough to melt it.

However, perhaps Daniel or Jesse can better answer this!