1.look alike,look-alike:someone who closely resembles a famous person (especially an actor)
2.Then,look alike always to be a adj,eg,A and B look alike:they look alike;
3.but look-alike always to be a noun:I had an excellent Prince William look-alike;
4.About look like,it is a verb,and the meaning is bear a physical resemblance to.
A looks like B,eg,Doesn't she look like her father?