Sometimes PL mounts can be stubborn. Typically, I find that if I very gently hold the lens and with simple low-pressure wiggle the lens 'up and down' while turning the PL collar with my other hand, 99% of the time it works.
Yes. Just rotate the PL mount collar counter-clockwise. If it won't budge, do what i said. I assumed you were having difficulty getting the lens off doing the proper procedure.