It's in the Eterna forest and you can catch Rotom there.
in eterna forest you need to get cut you can also find rotom at 12am if you go to the door upstairs first door two the left
go to old cheateu find a room w/ a tv press a
no
Magikarp
the Pokemon in diamond are sinnoh Pokemon i suggest http://Pokemon.marriland.com/diamond_pearl/pokedex to see all of them
in the old games of pokemon
only magicarp
In Pokemon Diamond/Pearl, you find a old man at route 212 with a Leafeon.
The old chateau is in diamond and pearl
10 years old
the old chateu is only in Pokemon diamond pearl and platinum versions
ROTOM! you can find the plasma Pokemon in the tv of the old chateau!!!