You can usually catch others Pokemon by using a Master Ball(does not always work)
Chat with our AI personalities
Not unless you have an action replay plugged into the back of your DS.
no but if you catch all the hoenn pokemon you can catch jotho and kanto pokemon
You are not allowed to catch other trainer's pokemons on any of the Pokemon games. You may only catch Pokemon from the wild or receive them through other means (events, game corner, eggs, etc.)
use the action replay and enter the X999 master ball cheat and catch other peoples Pokemon cheat and challenge Cynthia and get her Garchomp
You must first catch a Pokemon with pkrs which is extremely rare. If you want more Pokemon to catch it in the PC put the Pokemon with pkrs next to other Pokemon and they will catch it. Unfortunately it is complete luck if you catch a Pokemon with pkrs and there is no way of making one catch it exept for what i have put above. Hope i helped!