I managed to get access to RESET LENS CORRECTIONS DEFAULT. It worked a few times, other times not, sometimes back to nothing selected at all, and doing it manually. Seems random to me. Selecting it manually has worked fine for years. I'll just continue with that.
Actually colour management in Lr is pretty straight forwards. In all modules other than Develop Lr uses AdobeRGB for display purposes. In the Develop module it uses ProPhotoRGB Primaries, with a slightly different curve applied. IIRC it uses the same curve as sRGB. If you tick the Proof selection box then it uses which ever colour profile you have selected.
If you are working on a proof, and create a Proof copy then Lr should remember this, and is supposed to use this profile in the print module, instead of the default.
Lr colour management is actually a reasonably good pragmatic approach when working with RAW images. Fixed internal systems, and let you pick what to make that conversion to when you export to an RGB file.