This version of Candlekeep and the Candlekeep Library is only "visited" in the dream sequences that occur during the Shadows of Amn.
The first dream sequence only takes place in different cut-scene locations around the exterior of the Library and right outside the inner wall, while the second and third dream sequences take place inside on the fourth floor. The fourth dream sequence takes place both outside and inside the Library on the ground floor. The fifth dream sequence takes place inside on the second and fourth floors.
Exploration of the exterior and interior areas of the Library is not possible during the first three dreams or the fifth dream. The fourth dream sequence does allow for minimal exploration of the immediate area outside of the inner wall that surrounds the Library, and the ground floor area, but there are no lootable containers to be found due to the fact that this area is only a dream.