Yes, you're are correct about install.packages and install_version. I used install_version to install older version.
However, talking about managing libraries in Dataiku code envs. You provide an example how to select older version. It is here: https://doc.dataiku.com/dss/latest/code-envs/operations-r.html#manage-packages
but that example does not work properly. When I say properly I mean like install_version. For this function you specify exact version (let's x.y.z) and it installs version x.y.z. In your interface there's an option to do this (it is written like that) but it is not working. At first, I thought that Dataiku installs latest version available but later I tried some more examples and found out that it is not true. I don't how this stuff selects a version... It is shame because your functionality is not working or documentation is misleading (or even incorrect).