A:AnswerMore than likely no, as the FDA (or some government organization of health) doesn't allow public testing of in ear headphones, due to ear wax diseases and sanitation reasons. I am typically not a fan of in ear, but type headphones, but I must say that if the original airpods fit your ears these will almost certainly fit.
A:AnswerYes. The AirPods Pro case is the charging case. It also comes with a lightening to USB-C cable for charging. What you will need in order to make everything charge is the wall plug that will accept that USB-C plug (or a non- iPhone Pro charger with the wall outlet and cable).
A:AnswerThese are water resistant, no waterproof. While they can take sweat and splashing, as advertised, these are not advertised to be submerged. While they may survive falling into water with a relatively quick recovery, I would not bet on them surviving while swimming.
A:AnswerWhile the pass through feature on this divide can slightly enhance surrounding sounds, I do not know of a feature that would actually make this helpful as a hearing aid. Even in every day use, the enhancing of everyday sounds around me is very subtle.