I believe you meet him after completing the Sinnoh Pokedex. Then he will update your pokedex to national.
After completing the Sinnoh Pokedex, go talk to Professor Rowan. He will upgrade your Pokedex to the National Pokedex and give you the Poke Radar.
In the both the Hoenn and national pokedex, Pokemon number 367 is Huntail.
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once you have completed the pokedex, i am pretty sure you talk to one of the prof.[oak or alm] and they give you a gift.[mabye national dex]
Beat Wallace/Steven
number 152 is chikorita and send over to pal park from emerald, ruby , Sapphire after completing the national pokedex and talking to professor birch
Raichu
there are a total of 202 pokemon
Have to beat the elite four.
Chimecho
weedle
420
if national pokedex you go to the other gym leaders if normal pokedex you to the left at oldale town
Truthfully, I only know one, chicorita. You get it by completing the hoenn pokedex.
I believe you meet him after completing the Sinnoh Pokedex. Then he will update your pokedex to national.
Yes, if you trade it you will automatically get the national pokedex on Pokemon Emerald