"I know all" isn't correct, because it is incomplete. It leaves unanswered, "all what?". 'All' is telling you how much of something you know. All of it, some of it, none of it, etc. When you say: I know "blank", you need to specify what. I know 'a lot', would be fine, but not I know 'many' or 'any' or 'some'. I know all "blank". I know some "blank". All means every part of some group and you must specify the group.
Everything means all parts of all groups, all things. I know everything=I know all things.