I don't think you can, in emerald you need the nationaldex and POW! it's open but in ruby and sapphire you can't.
You can fish for a lanturn after you get the nationaldex at route 220 with a super rod.
Pokemon Ruby has Pokemon that Pokemon Sapphire does not and Pokemon Sapphire has Pokemon that Pokemon Ruby does not.
You can trade from Pokemon Ruby to another Pokemon Ruby using a link cable.
Ok People Im Not Talking About Pokemon Ruby!! Just Pokemon Ruby Destiny!
You get the diploma from catching all Pokemon from Nationaldex and Hoenndex.
you don't need to catch them just see all the Pokemon in the hoenn pokedex
I don't think you can, in emerald you need the nationaldex and POW! it's open but in ruby and sapphire you can't.
Starly.
u have to beat the nationaldex
You have to migrate it from Pokemon Ruby, Sapphire, or Emerald but to do so you need to obtain the nationaldex first ummm.... there's another way to get it, it's at route 210 north but you need to have a pokeradar=) hope that helped
You have to see all Pokemon Pokemon. But not the ones on nationaldex.
# Migrate It(Nationaldex needed)
find all 210 Pokemon on sinnoh pokedex then visit profeser rowan
At least 60 or more.
Defeat the elite four and become Pokemon champion with 60 Pokemon recorded in your pokedex.
Wait until there is a mass outbreak of Beldum after you get the nationaldex