If a process is linked as a reference, then this reference always has a certain version (can be changed in the Manage Used Models dialog), but it is only there for process documentation. Whereas during execution, the currently deployed version of the child process is always started, regardless of which version is linked.
If something goes wrong when starting (due to a mismatch of the actual version and the configured version), an Activity Failed Task is sent to the process owner of the parent process.
During initial deployment, the dependency tree must be deployed from below, which means the models that have no dependencies must be deployed first.
When a new version of a model is provided, a dialog is displayed that provides an overview of the models in which the current model is used. In addition, a message is sent to the process owner of the parent process that one of the linked processes has changed.