If I read that right you're looking for threads that have/haven't been answered? There's no actual function for that, threads are never marked as 'answered'. You can reply to any thread at ant time, the most recent threads always appear at the top of the forums, with info such as thread starter and date.
At the top of the forums there's a link with three dots. If you click there and go through to mark all forums read, then any time you come back any active threads with new replies will show up with their titles in bold letters. That's actually a wise thing for a new member to do, else everything looks new.