Question: Who plays 'the beast' in disney's live action movie beauty and the beast?
Disambiguated questions and answers: question: Who plays the young 'the beast' in disney's live action movie beauty and the beast? 
Who plays the adult 'the beast' in disney's live action movie beauty and the beast? 
answer:  Adam Mitchell
 Dan Stevens
Natural Questions answer: Dan Stevens (from the Wikipedia article "Beauty and the Beast (2017 film)")