Has had very little or no use and is like it was the day it came from the factory. It would be very difficult to tell the item from new.
Optics are as good as they get for a used lens.
Most used lenses will have some amounts of internal dust as they are not hermetically sealed units! The action of focusing and zooming over time draws dust in some more than others. While it might be a unwelcome addition to a lens the impact to image quality is minimal if any.
No internal dust that we can see.
Works with any camera with a PL mount