Yes, it is fully compatible with Canon EOS R-series cameras (like the R5 or R6) using an EF-EOS R adapter, and Sony E-mount cameras using a Metabones or Sigma MC-11 adapter.
No, the Canon EF 50mm f/1.4 USM does not have built-in Optical Image Stabilization (IS). It relies on the camera's IBIS or high shutter speeds.
Yes, the f/1.4 aperture is excellent for low-light video, though the USM motor may produce slight noise; external microphones are recommended for clean audio.