4.021 A proposition is a picture of reality: Because I know the state of things it represents if I understand the proposition. And I understand the proposition without its sense having been explained to me.

Tricky. How can I know or be acquainted with a state of things/state of things that does not exist (consider false propositions)? I think 4.021 must be taken as a tautology. To know the state of things a proposition represents simply is (i.e. means) understanding the proposition.