Pokémon Parallel Emerald walkthrough
10 parts, one per checkpoint Pokémon Parallel Emerald’s own documentation defines: the areas each one opens, the wild Pokémon and trainers in them, and the fight at the end of it. Everything here is read off the game’s own files, so anything it doesn’t state isn’t claimed.
Part 1: Before your first gym badge
10 areas · 40 trainers · Gym Leader Greta, Lass Tiana, Lady Cindy and 7 more
Part 2: Beat Greta — Rustboro Gym, badge 1
7 areas · 34 trainers · Gym Leader Brandon, Fisherman Elliot, Sailor Dwayne and 4 more
Part 3: Beat Brandon — Dewford Gym, badge 2
14 areas · 79 trainers · Gym Leader Wattson [Double Battle], Psychic Edward, Breeder Lydia and 14 more
Part 4: Beat Wattson — Mauville Gym, badge 3
10 areas · 74 trainers · Gym Leader Anabel [Inverse Battle], Hiker Trent, Picnicker Sophie & Bird Keeper Coby and 7 more
Part 5: Beat Anabel — Lavaridge Gym, badge 4
7 areas · 32 trainers · Gym Leader Noland, Cooltrainer Selina [Hail], Cooltrainer Pascal [Hail] and 4 more
Part 6: Beat Noland — Petalburg Gym, badge 5
14 areas · 94 trainers · Gym Leader Lucy [Poisonous Conditions], Gym Leader Lucy, Bird Keeper Josue & Ruin Maniac Andres and 9 more
Part 7: Beat Lucy — Fortree City Gym, badge 6
13 areas · 136 trainers · Gym Leader Tate & Liza [Permanent Psychic Terrain, Permanent Trick and Wonder Room], Bug Maniac Jeffrey [Rain, Permanent Grassy Terrain], Cooltrainer Marcel & Cooltrainer Cristin and 14 more
Part 8: Beat Tate & Liza — Mossdeep City Gym, badge 7
13 areas · 150 trainers · Gym Leader Glacia [Permanent Hail], Triathlete Sharon & Expert Auron, Cooltrainer Athena and 12 more
Part 9: Beat Glacia — Sootopolis City Gym, badge 8
6 areas · 54 trainers · Cooltrainer Albert, Cooltrainer Hope, Cooltrainer Edgar and 22 more
Part 10: areas the documentation doesn’t place
23 areas
It also doesn't say when 23 of its areas open up, so they are listed together in the last part rather than guessed into the story.