Part 13: Beat the Elite Four and the Champion

Beat the Elite Four and the Champion opens 12 areas.

Where to go

1. Haina Desert

   Wild: Sandile 70% · Lv 28-31, Castform 52.4% · Lv 28-31, Celesteela 50% · Lv 65, Gabite 47.6% · Lv 28-31 +2 more

2. Lake of the Moone

   Wild: Cosmog Lv 5

3. Lake of the Sunne

   Wild: Cosmog Lv 5

4. Melemele Sea

   Wild: Magikarp 78% · Lv 10-18, Gyarados 50% · Lv 10-18, Mareanie 50% · Lv 10-18, Finneon 40% · Lv 15-18 +5 more

5. Poni Coast

   Wild: Dugtrio (Alola) 100% · Lv 56-59

6. Poni Gauntlet

   Wild: Magikarp 59% · Lv 10-59, Barboach 40% · Lv 10-59, Dragonair 25% · Lv 10-59, Dragonite 25% · Lv 10-59 +11 more

7. Poni Grove

   Wild: Chansey 50% · Lv 52-55, Lucario 50% · Lv 52-55, Gumshoos 23.1% · Lv 52-55, Raticate (Alola) 23.1% · Lv 52-55 +5 more

8. Poni Meadow

   Wild: Magikarp 59% · Lv 10-57, Cottonee 50% · Lv 54-57, Petilil 50% · Lv 54-57, Barboach 40% · Lv 10-57 +7 more

9. Poni Plains

   Wild: Crabrawler 100% · Lv 54-57, Primeape 80% · Lv 54-57, Fearow 70% · Lv 54-57, Miltank 50% · Lv 54-57 +15 more

10. Resolution Cave

    Wild: Crobat 100% · Lv 54-57, Guzzlord 50% · Lv 70, Golbat 35% · Lv 54-57, Dugtrio (Alola) 15% · Lv 54-57

11. Ruins of Abundance

    Wild: Tapu Bulu Lv 60

12. Ruins of Conflict

    Wild: Tapu Koko Lv 60

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

It also doesn't say when New Mauville opens up, so it is in no part above; it has its own route page.