1. In the Color Grading tab in Lightroom Classic (not Lightroom), there is a small box on the bottom left hand side of the color wheels within in the Color Grading tab in Lightroom Classic. This allows you to use a color picker to select the exact color, from your photograph, that you would like to work with. It is incredibly helpful, but sadly, one of the only features I can see in LR Classic this is not in ACR.
2. This is incredibly valuable to any user, I would think, as it allows you to select and work with a color that is actually in your photograph, which is much preferred to a random selection from the color wheel.