Questions about Canon EF 50mm f/1.4 USM

They are identical products. However, the cheaper one is a direct import, which is not eligible for cashback. Otherwise, there are no differences in functionality.

Yes you can - it's an EF lens and compatible with your camera. You can also photograph cars with this focal length, depending on what kind of pictures you want to take. Minimum distance is 45cm, and 50mm on APS gives a focal length of 75mm which is a very slight zoom on what you see.

You can't answer that like that. What kind of videos? On the 90D, the 50 is a short tele with the angle of view of an 80mm lens.

Yes EF fits EF-S. Only the other way round does not fit and makes little sense.

Bei Canon unter: https://de.canon.ch/winter/

The Canon 50mm 1.4 is a little better made - but I wouldn't call the imaging performance an excessive improvement. On the other hand, I can recommend the Sigma Art 50mm - it has a much better image quality. Another candidate might be the Tamron 45mm 1.8 Di VC USD - it doesn't have a 1.4 aperture but it does have an image stabiliser.

No, unfortunately not. You need the Canon sun visor ES-71 II or DÖRR sun visor ES-71 II . Enclosed is an unboxing video: https://www.youtube.com/watch?v=VxSaTtFuvqQ

Yes, this lens is full-frame compatible.