To ensure that there are no conflicts in features and functionality, all team members should use the same version of the Unity Editor. Additionally, when a team member opens a project from a previous version of Unity in a more recent version, Unity updates the project files to the new version. These files might not be compatible with earlier versions of Unity.
When a new version of Unity becomes available, all team members should upgrade at the same time.
For more information on the impacts of upgrading a Unity project, see the Unity Upgrade Guides.