User blog comment:EmpyreanSmoke/Supernatural Q&A/@comment-207.126.210.191-20150905171102/@comment-24834479-20150907235219

1. Lilith would not have been as powerful as knights of Hell.

2. Yes, the story goes that she and Adam were married before she became a demon.

3. The writers either say Cain or Alastiar, but I think that it is Cain.

4. No, it couldn't kill a Knight of Hell, but it could kill Lilith.

5. This question I cannot answer. It could be anywhere from six thousand to eight million years ago.

6. No, someone with the mark cannot kill themselves with the blade.

7. I'm not sure whether or not it could kill death (as the darkness is still a mystery), but it could kill Archangels and Leviathan.