I have never even heard of one so if you heard it from someone else they weren't telling the truth
No, not all Pokemon in Diamond can learn Hyper Beam.
Hyper Beam.
You can buy hyper beam at the Veilstone Department Store.
No, there are second stage and even basic pokemon who are capable of learning Hyper Beam.
Hyper Cutter prevents a Pokemon's attack stat from being reduced by an attack from the opposing Pokemon (it can still be reduced by an attack from your own Pokemon that reduces attack).
In Pokemon Crystal, the Hyper Rod can be obtained by talking to the fisherman on Route 32, near the Union Cave entrance. The fisherman will give you the Hyper Rod as a reward for showing him a Red Gyarados, which can be found at the Lake of Rage. The Hyper Rod is a special fishing rod that allows you to catch higher-level Pokemon compared to the Good Rod or Old Rod.
yep every Pokemon can
Charmander must evolve into Charizard to learn Hyper Beam.
There is no such thing as a hyper ball if there is you cant get one in HG or SS
Gyarados learns Hyper Beam at level 50.
You can't get it in Pokemon Crystal. Though there are Pokemon who can learn it like Dragonite.
You can't use Hyper Beam in Kingdom Hearts. It is only in Pokemon.