2. What Did Klaus Do All His Life?
Klaus was well over one thousand years old when he died so he must have seen and experienced many things, no doubt, even if he spent a better part of his life running from his father who wanted to kill him.
There have been a few flashbacks into his past in the shows, for example showing his first meeting with Katherine or his life as a human with his family. But there are still a lot of unanswered questions about what Klaus did for most of the time he was alive, except learning how to paint.