For example, the game currently has 3 versions, 0.1, 0.1.1 and 0.2. I want them to be still playable even after releasing the new version. How can I do that? Can the files be stored in Devlogs so that would be possible?
The best method would be using butler which allows incremental patching and access to any previous version from the app.
For instance you can look at my game here
https://arekku.itch.io/foxes-and-cows
The download reads "Version 17" which means there are 17 versions you can download through the app by selecting which version you want.