Is there a chart on what versions of AutoCAD each version of Microstation will open?
Yes. See a table lists the support of RealDWG in different version of MicroStation in the [HELP].
What's New -> New in MicroStation V8i SS3 -> Data Interoperability Enhancements -> Autodesk RealDWG 2012 support -> RealDWG 2012.