Please include links to Wookieepedia when referencing creatures/characters whose names aren’t mentioned in the films (except for the ewoks of course).
Depends on who it is. Sentients like Darth Bane, Grand Admiral Thrawn or Exar Kun should be instantly identifiable names to any fan of Star Wars. Not knowing someone like Kas’im or Darth Talon is a completely different though.
I’ve never heard of any of those characters.
Well perhaps you should expand your horizon. Star Wars is so much bigger than the films.