Maya 2016 Extension 2 is not binary compatible with Maya 2016. To obtain the Maya 2016 and Maya 2016 Extension 1 API Guide, see http://www.autodesk.com/me-sdk-docs.
C++ plug-ins that were compiled against Maya 2016 or Maya 2016 Extension 1, including Maya 2016 service pack releases, must be re-compiled against Maya 2016 Extension 2 in order to be recognized by this version of Maya.
In addition, plug-ins compiled against Maya 2016 Extension 2 will either not load or exhibit unpredictable behavior if loaded in Maya 2016, Maya 2016 Extension 1, or any Maya 2016 service pack release.