its in cerulean cave but you have to get all kanto badges first
mewtwo
Yes, Mewtwo, Latios and Latias will be in HeartGold and SoulSilver.
Cerulean cave
yes, in the cerulian cave
A level 70 mewtwo.
in curelen cave you get mewtwo
in cerulean cave at the end
You can't catch Mewtwo in Pokemon Diamond and pearl and also platinum. But you can catch Mewtwo in heartgold and soul silver
you dont you battle mewtwo and get out
you dont, its not in HeartGold or SoulSilver, Ho-oh (HeartGold) or Lugia (SoulSilver) take their place. You can also get mewtwo
In Cerealean cave after you get all the kanto gym badges
Mew can't be catched in Pokemon heartgold, only mewtwo.