A legitimate "New Game" file cannot possess all Pokémon. Therefore, the user is seeking a modified save state —a file that appears fresh (e.g., in their bedroom, early plot point) but has been edited to include a complete Pokédex and storage boxes full of creatures.
Because the game is "new," you won't have HMs like Surf or Waterfall yet. The save shouldn’t break progression. However, including infinite-use TMs (like TM26 Earthquake) in the bag is a common courtesy tweak. pokemon emerald all pokemon save file new