If Monstro did not appear on your gummi ship map, there is a warp hole next to Wonderland. This should bring you to Monstro.
Generally Agrabah.
I'd suggest going by the Star Difficulty: Wonderland, Olympus Coliseum, Deep Jungle, Monstro, Atlantica, Agrabah, Halloween Town, Neverland, Hollow Bastion.
Kingdom hearts 2
Yes, monstro is in kingdom hearts, and he can be really confusing. just go in the door that riku went through (watch the cutscene) and everything else is pretty straight forward, just don't try and jump any gaps.
After you beat the Parasite cage once.
You can't.
roar
No, he does not
Probably Agrabah
Generally Agrabah.
By defeating Jafar.
The original 3 and Aladin
They are in Agrabah and Neverland (Clocktower)
I'd suggest going by the Star Difficulty: Wonderland, Olympus Coliseum, Deep Jungle, Monstro, Atlantica, Agrabah, Halloween Town, Neverland, Hollow Bastion.
Agrabah from fire type heartless
Agrabah
you need to lock the keyhole in Agrabah, by beating Jafar.