The DockPanel is designed to be used only with DockingManager. The prevention of a docking operation is possible only with the global DockingManager property AllowDocking and it's applied to all hosted IDockable windows.
We are planning to extend the RadDock component to setup an allow operation for each IDockable window. Once this is done, your scenario will be possible.
When the DockPanel is in floating state, the unpin operation is invalid. This is an issue in the current RadDock component and will be addressed in our next release.
Thank you for the feedback. Your Telerik points have been updated.
the Telerik team