Is there a question on the main site about taking automatic backup of Android apps whenever they are installed or updated? The backed up file should show the version code or version name of the corresponding apk.

I want to keep APKs of all the apps I ever update or install, so that I end up in a position to switch to whatever version I like without bothering to download a previous version of an app from some third-party site.

I know Titanium Backup can take backups but it does it periodically and I can't differentiate between versions.