"a must" - a required thing "a given" - something that is well-known to be true or required "transitional skills" - in this context I interpret this to mean "the skills required to transition to a different role to one's normal role" The sentence form means that "transitional skills" are "a must" (required) and "proper style" is "a given" (also required). Both "transitional skills" and "proper style" are required for the part that he plays in the movie "XXX". The part after the comma implies that despite these difficult things being required, the actor was still able to put on an impressive performance.

Hi there, Bob. I'm not sure what they mean by "a given and proper style a must". Is it a must to have "transitional skills" if you want to have "a given and proper style"?

What is the question Maciej?