Can an old photo from Gmail get put into my photo stream? Is it possible for an old photo from gmail (like 6 years old) to be put into the photo stream after an update? A very old picture appeared in my photo stream and I don't know how it got there.
Yes - software does have bugs from time to time. It also could be you unintentionally did it or that another device is signed into your iCloud and entered that photo intentionally.