How do I download full resolution photos on my iphone (8+) to use offline? I used to keep all of my photos (literally 40K or so) on my iPhone. I did eventually fall into the iCloud trap, and have still not figured out a way to assure that a healthy number of my full resolution photos will be available to me when I am on a plane: the one time I know I'll have 5 hours with nothing to do but edit photos from the last decade. I know that "recent" full resolution photos are stored  on the phone, but going back to what date? And how does that help if I choose a  picture from 2014 to edit? Thoughts about how to edit while in "airplane mode?"
You can download the full resolution photos to your phone by going to Settings -> tap on your photo -> tap iCloud -> tap Photos -> tap "Download and Keep Originals" (instead of "Optimize iPhone storage"). You will, of course, need to have enough space on your phone to download all photos.