#1: As far as I know, Apply Auto from prefs does an auto adjustment as the image is is rendered when making the initial "default" rendering for Bridge. Once the full raw image is loaded, if the full raw data results in a slightly different Auto analysis, the Auto button will be enabled and the Auto is run on the full raw data and you'll get a similar but different result. I've seen images that come in with the Auto prefs enabled where the Auto button is dimmed meaning the initial and full res analysis is the same.
#2: If a native raw and a DNG of that raw file are in the same folder, ACR will use the .xmp sidecar file as the image settings–even if there are xmp settings in the DNG. Setting the prefs to ignore side car files means there will be no conflict.
#3: primarily used when some other application has made image settings to the raw image. Principally useful for clearing settings from raw files touched by ACR hosted in Elements (as far as I know) because Elements ACR only has a small subset of all potential ACR settings.
#4: The Camera Calibration settings are designed for adjusting the sensor calibration for sensors whose color rendering differs from the sample tested by Adobe. The calibration sliders are actually depreciated now because they predate DNG profiles. Thomas was ready to rip them out (back when DNG profiles went in-ACR 4.6/5.0) but was persuaded to keep them for creative purposes by Martin Evening (and me) because they could be used for color FX like cross-processing. There is very little likelihood there will be any changes forthcoming because, well, DNG profiles offer superior color calibration rather than manual slider adjustment. So, I suspect you'll just have to learn to live with what is there now-unless you have some evidence that DNG profiles don't provide a superior calibration.
1. Thank you for the trick ...
2. I tried your case and also tried the case in the book of Martin Evening (there is a different example from yours), but I could not see any difference that this option creates. Maybe, I'm missing something ... I think that Reference document should be more clear. It talks about a completely different case as far as I can see.
3. I don't have Elements ... I tried it with the Lightroom (after saving adjustments to the file), but it is still inactive. Maybe you mention another third-party program ...
4. I studied ACR for learning the functions of every single checkbox, every single menu items and every single sliders ... and for learning their meanings of course (for this purpose, I read three books and a bunch of websites in two months about the color theory and management - I think I need to reread though). So, I'm just looking at how all these sliders consistently work. Thank you for your explanations.
By the way, as you see, my English is not so well and sometimes I can not be sure whether or not I choose the correct word for expressing myself.
Thanks a lot for all these explanations.