What speed limits can this road possibly have is a question I want to ask about this specific road. Yet this can be answered by referring to the country, which is already known when you create the road. But the user that asks this question can still ask this about roads in different countries, so this question still is valid.

Different objects can have different methods. When the method to be used is known at the time of object creation it can be chosen by assigning the appropriate function pointer in the vtable. The method itself might not necessarily need a instance pointer though.