In the movie, the door leading down to the basement is directly under the stairs. In the first Beethoven film, the door to the basement wasn't there. Instead there were drawers and a cabinet in the wall.
At the carnival, when Janie orders ice cream, she has her hair in a pony tail. When she walks away and the bully follows, her hair is down.
When Regina orders her boyfriend to take Missy, he puts the leash around the dog. The close up is of a woman's hand, complete with red nail polish.
When Ryce is figuring out what to wear to school, she is holding up a dress in the mirror. She asks Beethoven what he thinks about it and turns around. When she turns around, she's holding up a different dress.
After Regina gets the stump off of Floyd's head she falls down the hill with the stump. The next time we see her, the stump is gone.
In the first two shots of the scene when Beethoven and Missy are walking down the streets, we can see them tied together by their collars with a piece of fishing wire to keep them walking in sync.
When Beethoven leaves out of the basement window after the family leave, you can see a wire on top of the door to assist the dog in pushing it open.
When Emily is praying before she goes to bed, she says that George wanted to give away the puppies when they get bigger, but it was actually Ryce who suggested that.
When Taylor locks Ryce and himself into the bedroom of the cabin she goes to leave and he has locked the door. She says to him did you lock the door and he holds up keys. But the doorknob is a standard doorknob with a turn lock on the doorknob so she could have just unlocked it and there were no keys involved.