I can't downgrade my adobe's apps...

1. Open CC Desktop app.
2. Click the gear icon.
3. Click on Apps.
4. Scroll down to Settings.
5. Check the box to Show Older Apps.  See screenshot.

Pre-2019 versions are no longer available.

Adobe only offeres the current and ONE older version

If you have an old operating system and can't run the current version check the link below... and if this is the case and you do find a download for your old operating system be sure to copy the download to at least one external device in case Adobe completely removes the download

Direct Download Links https://prodesigntools.com/tag/ddl

Are you running a trial? Old versions only available if you subscribe. 

Is the Creative Cloud application updated to the latest version?

-Manan