Question: Select All option in Photos at iCloud.com
When downloading photos from icloud.com, you can only download one item at a time, it doesn't have an option to mass download all photos from there.
Only option is you have to use Photo Library on PC to mass download Photos.
--If user connects iPhone to PC via cable, some photos are visible there and not all. So you couldn't even download all photos from there as well.
--Also why some of the photos are backed up to iCloud and some aren't?
--Then we have to delete the Photo Library application when our work is done.
If iCloud lets you download one photo, it should have option to Select All photos for downloading purpose.
After discussing with Apple Support, they don't have any reason why this feature is not supported.