Yes, for sure! It's not very big, but it good!
Yes. It's available for the guests.
I believe it's for guest use only.
I have used the pool when we stayed and it's not worth getting into your swim wear as it's like a metal tub.
The pool is located end of the sky bar/restaurant and if you need to go to bathroom you have to get dressed as they don't like you to walk past the other guests eating. So bit of a bad layout.
Get an answer from Hotel MIM Sitges staff and past guests.