It's impossible. You can't. In FR/LG you can catch Johto Pokemon in the Sevii Islands, and trade from there.
You can't. It's impossible.
you can, but you need to pass the elite four, give some guy a ruby and a sapphire, and you need a rainbow pass and a national pokedex to do so.
Time capsule
by going to the time travel trading on the far right you can trade from and to Pokemon yellow, red, and blue