A:AnswerIt is an APS-C lens. It says so right there in the downloadable owner's guide: "This lens can be used with Sony α camera system E-mount (APS-C format) cameras."
Even the description on the Best Buy site says, "The wide-angle design features a 24mm equivalent focal length" (16mm * 1.5 crop factor = 24mm).
A:AnswerWhy ask a question with a false premise? I haven't tracked its availability since you posted your question, but it is available now and also on sale. Bear in mind, also, that availability varies by location.
A:AnswerNo adapter needed. BUT the autofocus noise is REALLY loud so if you do video it’s going to ruin the sound. Search for Signa 16mm autofocus noise and you will hear it