1) Class is a template or blueprint that have functions and member variable. Object is an instance of class. When we create an object than a memory is allocated to that object. This memory is equivalent to the memory of member variable.Exception is if member variable is static than it is shared among all object.functions are loaded once in a memory and shared by every object. sharing of function is done with the help of "this" pointer.
2) Yes. The size of int is always same. The size of int depends on compiler and processor.
Book : Herbert Schildt c++ complete reference
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