I do not know where to find past releases of Docker images. (Someone else on this support board probably does know however).
I am not sure I understand why you are asking for an older release, given the error message that you are seeing.
If you see an error saying "The document format version X is newer..." then it means that you need to be running a newer version of Skyline.
If you are using a new version of Skyline and you need to save your file so that it can be opened by an older version of Skyline you can use the menu item "File > Share". There is a dropdown on the Share Document dialog which lets you choose to save in older version formats.
If you want to install an older version of Skyline on your computer, you can start from the "Unplugged" installer page:
After you click "I agree", there is an "Archive" link which will allow you to download older versions of Skyline.