We not only never saw the Beasts’ human form until the end of the movie, we didn’t even get a clear shot of him as the Beast until Belle meets him at the end of the film’s first act.
We never saw their human forms in the animated version of the film until the end.
A lot of people were surprised when marketing materials for Beauty and the Beast were released that showed the human forms of characters like Lumiere and Cogsworth.
All of the backstory is given to us as narration over still images that are shown as stained glass windows.