Yes, it features a dust- and splash-resistant structure with a water- and oil-repellent coating on the front element for shooting in harsh conditions.
Yes, it is natively designed for Sony E-mount full-frame cameras, including the A7 IV, A7R V, and A1.
The Mark II is 7% lighter, features a faster HLA autofocus motor, improved edge-to-edge sharpness, and adds a physical aperture ring.