I heard that BIOS shadowing works by copying the BIOS program into faster memory and running it from there. Is that correct? BIOS is responsible for certain startup tasks, so after startup, does it get unloaded from memory?
You are correct BIOS shadowing simply loads the BIOS into Memory for quicker reference. I could not find much use for it after startup, however according to Microsoft it will stay in memory after startup. Apparently DOS used the BIOS to write to the screen. From the MS article:
This article is a little old but still relevant since newer versions of Windows do not reference the BIOS after boot. Source