All main-sequence stars are in hydrostatic equilibrium, where outward thermal pressure from the hot core is balanced by the inward pressure of gravitational collapse from the overlying layers.
Nope. Not in stellar metamorphosis.
All stars which are plasmatic (shine in the visible spectrum strongly), are NOT in hydrostatic equilibrium. They are gravitationally collapsing. This gravitational potential energy feeds the non-spontaneous chemical combination reactions which begins the formation of molecules from their elemental counterparts.
The center of the star is very, very low pressure and is increasing in pressure as the shell contracts and the star evolves.
All young stars are hollow structures. They do not possess nuclear cores.
As the shell contracts, the star cools and shrinks becoming the "planet".