In the trophy garden (below hearthome city)
No, that is only avilable for Pokemon HeartGold and SoulSilver. But a Shiny Pichu can be obtained in any game with Pichu in it, but it's really hard to find.
pokemon breeder in route 210 he has pichu, happiny,pikachu
you can get it in the trophy garden in the Pokemon mansion in route 212 or you can breed a Pikachu or Raichu.
pichu
cleffa
Maxed out happiness
cleffa
Trophy Garden. You can also get Pichu there.
in pokemon pearl/diamond it is in the trophy garden
pichu in Sinnoh Dex exeggutor in National Dex
empolion and have starly ,bidoof and pichu
Usually somewhere after lv. 20.