The subject is my only question. When sitting normally, does the pressure/force from the pants on the foreskin cause it to fold inwards, or anything of the sort?
It varies. Why? Because foreskins come in different lengths.
Normally the foreskin will fully cover the glans when not erect. As you start to get erect the end of the urethra (meatus) becomes visible and the inner layer of the foreskin is exposed.
Again, everyone is different. Hope it helps.