I have no idea what you're talking about. Pokémon don't inherit base stats. All Beldum have the same base stats: HP 40, ATK 55, DEF 80, SAT 35, SDF 60, SPD 30.
Assuming this hasn't changed from Ruby/Sapphire, a pokémon inherits three of its IVs from its parents and the other three are random. Also, which three are inherited is random. IVs, Individual Values, are values between 0 and 31 that give your stats a slight boost and are different for every pokémon; they create stat variety within a species. There is no way to alter a pokémon's IVs.
As for your last question, chain-breeding is typically done for either of two reasons. The first is to achieve a certain move set, but since Beldum can only breed with Ditto, it doesn't have any Egg Moves. Thus, you wouldn't ever chain-breed Beldum for that.
The other reason pokémon get chain-bred is to try to achieve a descendent with perfect IVs; an IV of 31 for all six stats. For example, if you had a Ditto with at least two, ideally more, IVs at 30 or 31, you might breed that Ditto with a Beldum, hope the child inherits a 31 or two, then breed the child with the Ditto and hope the baby inherits 31s from both parents. Of course, since three of a child's IVs are completely random anyway, perfection is hard to come by.