Is close to new condition and although is being sold as used it probably has had minimum use. It would have very minimum signs of wear or cosmetic blemishing.
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.
Very few small specks.
Works with all Pentax AF / DSLR cameras, compatible with full frame