you get them by catching all 200 Pokemon
The only 2 ways to get johto starters is to see all Pokemon in emerald, and beat mt.battle in Pokemon XD and then send them to ur gameboy adv.
Yes you have to trade because you can't get all the Pokemon alone.
Technically, yes you can get all the Johto starters... mainly one from the Emerald versions if you have completed 202 entries of the Hoenn dex, Birch will give you a "surprise" and you can choose one of the Johto starters. But that's one way to get them, though that'd take quite some time to achieve that... But to get the other two, you might have to trade with your pals or from Colosseum/Gale of Darkness.
cindaquil must be migrated from emerald version... in emerald, once you catch all the pokemon, the professor offers you one of three pokemon... you may pick from the johto starters (cindaquil, chikorita, and totodile)
All Pokemon from Kanto, Johto, and Hoenn can be obtained in Emerald. Susrskit, Masquerain, Meditite, Medicham, Roselia, Zangoose, and Lunatone must be traded from Ruby or Sapphire. Other Pokemon like all of the starters must also be traded over.
you can get them by either filling all your pokedex in emerald and talk to professor birch and then migrating them or AR.
Basically, -just- and I use the term loosely, obtain all Pokemon obtainable in Emerald/ruby/sapphire, on such games, then choose a johto starter (Birch will call you) and trade. Only way, sorry.
You can get Totodile In Pokemon FireRed(Johto Starters).In GBC You cant get IN Pokemon Gold,Silver,Crystal.Not sure if in Ruby,Sapphire Emerald.
Sorry, but the only way to get all the starters from Pokemon Crystal to Fire Red or to Pokemon Emerald is to get a gameshark and do it from there.
cheats
To get Johto starters, you have to use Emerald Version. You have to complete your Hoenn Dex (get all 200 pokemon) and you have to choose one of the three. Then (if you want them all) you restart the game and get them all again and choose a different one. sorry it's so hard!
No, you need to trade or transfer them from Emerald.