The 3ds Max 2014 SDK is binary backward compatible with the 3ds Max 2013 SDK. Therefore, you can run plug-ins compiled with the 3ds Max 2013 SDK in 3ds Max 2014 without recompilation. The changes in the 3ds Max 2014 SDK are mostly additions and extensions.
3ds Max 2014 is only available in the 64-bit version. See SDK Requirements to know the platform requirements for building plug-ins in 3ds Max 2014.