Continuity mistake: Near the end, as the objects arrive and are watching as Belle helps Beast lie down, the rose stem is shaped as a question mark. A few seconds later, viewed from the same direction, when the last petal falls the rose stem is now shaped as a reversed question mark. (01:14:40)
Continuity mistake: Gaston wears a quiver in the scenes where he is after the Beast, and the brown quiver strap runs across his body over his red shirt. After Gaston stabs the Beast with his knife, the brown strap and quiver is still on. However it then cuts, and as he starts to fall, the brown strap of the quiver has gone. Then in the next shot the strap is back on, over his red shirt. (01:16:15)
Continuity mistake: After the Beast is stabbed, and is on the floor dying, Belle is at his side comforting him. In one shot her hand is stroking the left side of his face. It cuts and suddenly her hand is on the right side of his face. Then a few shots later, she puts her left hand on the right side of his face, but when the shot changes her hand is back to her side. (01:16:40)
Continuity mistake: When the Beast briefly dies at the end of the film, before being turned human, Belle cries and lays down on his chest, with her head resting on his red cape and her hand clutching it. However when it cuts to a closeup, Belle's head is suddenly resting further down, on his white shirt, and she is clutching the shirt now too instead of the cape. (01:17:35)
Continuity mistake: At the very end, when all the objects change back into humans, the position of the roses on the walls in the background changes between shots. (01:23:25)
Continuity mistake: At the end of the song "Belle", there's an overhead shot in which you can tell that there is no mud on the street in front of Belle. Then a few seconds later, there is a big puddle of mud, and Gaston throws her book into it.
Continuity mistake: When Gaston has his feet on the table, the amount of mud on the book and tablecloth changes between shots.
Continuity mistake: When Gaston proposes marriage to Belle, there is a thick pink cushion on his chair. But when Gaston sits on it and puts his feet on the table, the cushion is much thinner, and it is now red.
Continuity mistake: The amount of snow on the stairs of Belle's house constantly changes in the scene where the villagers try to take away her father.
Continuity mistake: The eagle in the bar constantly changes size throughout the "Gaston" song.
Continuity mistake: The doors to the fireplace are ovalish with triangular tops when Cogsworth says "No tea, no tea." When the Beast bursts in, they are rectangular.
Continuity mistake: At all times, the enchanted rose is on a smooth marble table, except for when the Beast roars with pain after Gaston shoots him with an arrow. In this shot the table is wooden.
Continuity mistake: Just after the Beast tears the painting, look carefully out the window and you'll see a carving of a person with his mouth open on the balcony. Then when the shot zooms out of the castle, this carving is gone.
Continuity mistake: At the start of the song "Kill the Beast", the mirror keeps coming closer and further away from the buckle on Gaston's belt.
Continuity mistake: Belle takes a blue book from the library, but in the shot where Gaston sings "I'm making plans to woo and marry Belle" the book is now brown.
Continuity mistake: When Belle is reading her book inside, there is a black teapot over a plate on one of the shelves. Moments later, the plate is to the teapot's side.
Continuity mistake: When Maurice enters the castle, the front doors have four planks each. For the rest of the film, they have five planks each.
Continuity mistake: The width of the grey rings on Maurice's lantern changes in the scene where he is lost in the forest with Phillipe.
Continuity mistake: When Belle is reading her book by the table, a shelf over the fireplace is visible below another shelf to the left of it. Moments later, after Gaston has entered and Belle asks "What do you know about my dreams?" this shelf is above the shelf to the left of it.
Continuity mistake: After Belle sees the painting in the West Wing, there is a shot of the table where the enchanted rose is. In this shot, the magic mirror is not on the table. In the next shot, it is. Then when the Beast yells "Get out." it is gone again.
Answer: In the prologue, it states that the Beast must find true love by his 21st birthday, and that he had been cursed for ten years, so since his relationship with Belle takes place as the deadline approaches, he must have been 10 when he was cursed.