You have to own 60 Pokemon to get the national pokedex.
No, really you have to only own 60 or more
you cant... yet
There is no special Pokemon you have to own, in leafgreen you must own/ have owned 60 Pokemon but say which game in the question...
the mystery gift but u also need a friend with a wireless adapter or get ur own cables
If you have 60 Pokemon or more after beating the game oak will give you the national dex which will allow you to catch and own johto and hoenn Pokemon.
No but if you own an Action Replay you can use codes to play as others
if you own a Pokemon lets say magikarp the red areas on the map on the pokedex are where you can find it.
Dive is not an HM in leafgreen however some Pokemon can learn it on there own, if you want to have a Pokemon with dive have the Pokemon that you want learn dive in ruby or sapphire or emerald then have them trade you it and now you can use dive but not outside of battle because its not an HM.
Unfortunately, you can't get an Onix in Pokemon Emerald. To have your own Onix, you need to trade it from FireRed or LeafGreen. Hope I helped :)
he doesn't evolve on his own you have to trade him with one of your friends and then trade him back
That's not possible you have 1/8000 chances to see one your lucky if you do i did twice and i own one right now.
you can't.:( but you can trade it from firered or leafgreen but to do that you have to get the national dex by catching 60 pokemon and getting all the items the aide has for you.if you own firered or leafgreen just go to google andtype in how to get MEWTWO. hope this helps:)