With your updated question, use combination of pre-processor directives to achieve this:
within your DLL:
#define DLL_VER2
within your application (your DLL must be set as a dependency at this point, that'll make it compile first):
#ifndef DLL_VER2
#error The current application requires DLL_VER2 for compatibility.
#endif
Of course, make sure that your error statements will make sense to the other developers.