About model and data exchange with 3rd party solutions: Revit, Solibri, dRofus, Bluebeam, structural analysis solutions, and IFC, BCF and DXF/DWG-based exchange, etc.
You have to "Save as" to the AC 9 format from AC10. Some elements may be lost if you have used tools that are new in 10. I'm not sure about saving the layouts back to PM9.
