Can someone please list how to get to each region it at least point me in the direction of where it is if it's on previous pages or something? I haven't played since 6b and I just remember being stuck with maybe just five regions despite seemingly having more based on characters and badges with blank spaces missing.
Here's what I gathered from a short time running around with cheats enabled. It seems like Johto and Unova serve as the bridge between the Japan inspired regions and the Europe inspired regions. Still haven't found the way to Alola yet.
Kanto
Saffron City - Train Station (Johto, $100)
Johto
Goldenrod City - Train Station (Kanto, $100)
Goldenrod City - Airfield (Unova, $5000)
Olivine - Olivine Port (Hoenn, Sinnoh, $200)
Hoenn
Dewford Town - Dewford Port (Johto, Sinnoh, $200)
Sinnoh
Canalave - Canalave Port (Johto, Hoenn, Fullmoon Island, $200)
Unova
Mistralton - Airfield (Johto, $5000)
Castelia City - Cruise Dock (Kalos, Galar, $200)
Virbank City - Virbank Port (Kalos, Galar, $200)
Kalos
Coumarine City - Coumarine Port (Unova, Galar, $200)
Galar
Hulbury Town - Hulbury Port (Unova, Kalos, Isle of Armor, $200)
Wedgehurst - Train Station (Crown Tundra, $100)
Hisui
Use Dialga (works from any region)
(May be other Pokemon, haven't tested it further.)