A: There are large general-purpose mounting blocks for vinyl siding. They are essentially a rectangular surface with J-channel molded into the sides. So you could use one of those, or you could trim it out with J channel. If you're going to do this right, you have to flash the wall penetration behind the vinyl anyway, and relative to that the J channel seems like a minor annoyance to me.
A: This product is designed for use as the outside sidewall termination of Kitchen, Bath and Dryer exhaust systems.
A: Yes, this model seals well.