Yes, it is a professional L-series lens with weather-sealing against dust and moisture. However, for full protection, it is recommended to use a 72mm front filter.
Yes, it works seamlessly on Canon EOS R-series mirrorless cameras using an EF-to-RF adapter, often benefiting from the camera's Eye-AF for better focus accuracy at f/1.2.
The lens uses a heavy glass group; while accurate, the AF is slower than modern Nano-USM lenses. It is best suited for controlled video shots rather than fast-moving action.