Missingno is not avalible in Pokemon Diamond without help of the Action Replay.
no you have to get is from an action replay or go to a Pokemon event
You can't.
There is a way to do it without cheating. Just simply trade a Pokemon that knows fly. Example: you have a staravia in Pokemon pearl that knows fly. Just trade it to Pokemon diamond.
yes
Dialga
You can get a Cyndaquil without trading only by transfering it from a GBA Pokemon Game onto your Pokemon Diamond Version.
no
no
i have Pokemon diamond, and played 600 hours. its not possible. but you can catch a ditto, and make Pokemon eggs.
you cant get it without migrating.
trade with Pokemon Platinum
Rival
you do need cheats
You can't without cheats.
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no