Beauty And The Beast Poor Beast

So it s clearly stated in Beauty And The Beast that Beast is 21. Lumiere also says they ve been cursed for 10 years. Which means that the poor orphan Prince was only 11 when that witch dresses up like a hobo, barged her way into his home, and then got annoyed when he was rude to her and decided to destroy his life in the process. It also begs the question, why is there a painting of the adult Prince hanging on the wall? How is that even possible? Was it just a lucky guess, like when you do that age composite thing online to see what you d look like as an old person?