The distance from the Sun at which an asteroid is considered a comet is not solely determined by its distance but by its behavior and composition. While many comets originate from the Kuiper Belt and the Oort Cloud, both located in the outer regions of the solar system, not all objects within those regions are comets.
Comets are typically characterized by their icy composition, consisting of water ice, frozen gases, dust, and rocky material. When a comet approaches the Sun, the heat causes the ice to vaporize and release gas and dust, creating a glowing coma around the nucleus and often forming a visible tail.
On the other hand, asteroids are rocky or metallic objects found predominantly in the inner regions of the solar system, mainly the asteroid belt between Mars and Jupiter.
So, it's not solely about the distance from the Sun but about the composition and behavior of the object. An asteroid that exhibits cometary behavior, such as the release of gas and the formation of a coma and tail due to heating, would be considered a comet, regardless of its distance from the Sun.