Instructions
Capture any missing Pokemon from wild grass or caves, or by fishing. If you have seen the Pokemon but have not yet captured it, your Pokedex will reveal the location where that Pokemon is able to be captured. Additionally, you can trade with your friends for any Pokemon you are missing.
Trade Pokemon from "Pokemon Ruby" or "Pokemon Sapphire." There are seven Pokemon that need to be traded from the previous game. They are Surskit, Zangoose, Lunatone, Meditite, Medicham, Rosealia and Masquerain.
Capture any legendary or hidden Pokemon. Some Pokemon, such as Groudon or Kyogre, can only be captured after you have defeated the Elite Four. You will only have one chance to capture these Pokemon --- if you defeat them without capturing them, you cannot complete your Hoenn Pokedex.
Travel to Littleroot Town and speak to Professor Birch in his laboratory after you have caught all 200 Hoenn Pokemon and completed the Pokedex.
Select either Cyndaquil, Totodile or Chikorita as your reward. (You may choose only one of these Pokemon.)