How do you get fire type on Pokemon Diamond?

Answer 1

Sadly, you don't get to fuse Pokemon in those games. There's only one game that allows you to do so in some capacity (Black 2 and White 2), and even then, it's only one Pokemon (Kyurem) that can do so.

Answer 2

Apparently, it's possible.

If you make the three legendary Pokemon of the lakes level up at the same time using exp share or something like that, they morph into the ultimate Pokemon.

Answer 3

You can't get a fusion Pokemon in any Pokemon game. Wherever you got this idea check your sources.

Answer 4

The only fire-type Pokemon available before getting the National Dex are the Chimchar set, and Ponyta/Rapidash. Otherwise, trade over from someone with fire types, or find an alternative.

Answer 5

It requires action replay for soulsilver version. You use action replay to get the pokemon, then trade them to your diamond version, and there you go.