Sculpture in the Expanded Field

Question 1: It was said in the article that sculptures are a "historically bounded category" and have their own internal logic. But when the article began to discuss when the logic fails, and there is negative condition ("a kind of sitelessness, or homelessness, an absolute loss of place"), I was a little confused. Why is it that if "multiple versions can be found in a variety of museums in various countries," that this sculpture loses it's logic? Does it not have its own logic in itself? Why does it have to be based on other pieces of art?

Question 2: What is the difference between a sculpture and a monument? Is it that the sculpture becomes a monument when it represents something or stand for something (maybe in memory of history?)? When do you know a sculpture is a monument; is it not one when there is negative condition? Is it only a monument when the piece has logic?