While ejbStore() and ejbLoad() etc. methods are declared in
EntityBean interface. Where ejbCreate() and ejbPostCreate() methods are declared.

ejbCreate() and ejbPostCreate() method signatures wholly depend upon the what you are going to declare in the Home Interface. To my knowledge they are developed when creating the Stubs and Skeletons.

You need these methods to create an EB, but they are not declared in the EntityBean interface. It's not possible, you see: an EB would have a create method that takes 3 strings for initialization, another would have a create method that takes a single integer *and* another create method that takes an object of type X. Declaring ejbCreate and ejbPostCreate for all combinations of number of parameters and parameter types is simply not possible.

The container, however, checks if they exist and are compatible with the create methods in the EB's remote interface.