Part 3: Beat Brawly — Dewford Town Gym, badge 2

Rock Smash (HM06)

Beat Brawly — Dewford Town Gym, badge 2 opens 3 areas.

Where to go

1. Slateport City

   Wild: Pikachu Lv 20

2. Granite Cave

   Wild: Zubat 60% · Lv 6, Aron 40% · Lv 6, Makuhita 29.6% · Lv 6, Geodude 25.9% · Lv 6 +2 more

3. Route 110

   Wild: Magnemite 57.1% · Lv 6, Minun 38.1% · Lv 6, Plusle 38.1% · Lv 6

Everything you can have caught by this checkpoint · Open the interactive guide

It also doesn't say when 9 of its areas open up, so they are listed together in the last part rather than guessed into the story.