What if Ash was sent back in time after becoming world champion because the world was ending because of Cyrus?
What if the new timeline was made of a mixture of the anime, "I choose you" movie verse, manga, origins, and games?
What if Shadow Pokémon existed in the new timeline?
What if Ash caught some of the Pokémon red caught in the Manga?
What if Ash kept his key stone, Z-ring, Dynamax band, Lucarionite and Z-crystals?
What if Ash also got a Venasuarite and a Charizardite X (Pokémon origins Red)?
What if all of Ash's Pokémon remembered the old world and went to join/find Ash?
What if all of Ash's Pokémon were in the form he originally met them in when they went to find him?
What if the rotom phone was the main Pokedex/Phone in the new world?
What if Ash could understand all Pokémon and use aura in this new world?
Also manga characters could be in the story.
Ash:
Pikachu (G-Max)
Butterfree
Pidgeot
Bulbasaur
Charizard [Possible Mega X]
Squirtle
Kingler
Primeape [Possible Anhilape]
Muk
Tauros x30 [Some can be made Paldean with some flame and aqua breed]
Mr.Mime [With Delia/Mom]
Lapras
Snorlax [Can G-max thanks to Master's EX red]
Heracross
Bayleaf
Quilava [Possible Hisuian Typhlosion]
Totodile
Noctowl (Shiny)
Donphan (Egg)
Swellow
Sceptiple
Torkoal
Glalie
Staraptor
Torterra
Infernape
Buizel
Gliscor
Gible
Unfezant
Oshawott [Possible Hisuian Samurott]
Pignite
Snivy
Scraggy (Egg)
Leavanny
Palpitoad
Boldore
Krookodile
Greninja (Bond phenomenon)
Talonflame
Hawlucha
Goodra
Noivern (Egg)
Rowlet [Possible Decidueye/ Hisuian Decidueye]
Lycanroc (Dusk)
Incineroar
Naganadel
Melmetal
Dragonite
Gengar (G-Max)
Lucario (Egg, Mega)
Sirfetch'd
Dracovish
Red:
Poli (Poliwrath)
Saur (Venusaur, Mega) [Can be Bulbasaur]
Pika (Pikachu) [Can be Pikachu]
Snor (Snorlax) [Can be Snorlax]
Gyara (Gyarados)
Aero (Areodactyl)
Vee (Eevee) [Can change between all eeveelutions or becomes a permanent Espeon]
Timeline:
Kanto
Orre
Orange islands
Johto
Hoenn
Kanto battle frontier
Sinnoh [Can possibly go to Hisui]
Unova [Ash takes a challenge to get all 10 unova badges in this order; Trio, Basic, Toxic, Insect, Bolt, Quake, Jet, Freeze, Legend, Wave]
Kalos
Alola [Ash could take the island challenge again and get the Z-crystals he never got (Fightium, Flyinium, Waterium, Ghostium, Bugium, Darkium, Psychium, Iceium, Groundium, Dragonium, Fairyium, Electrium[One that doesn't become the Pikashium], Pikium, Eeveeium, Snorlium, Incinium]
Galar/World [Can take Galar gym challenge]
Paldea
(Means kept)
[Means suggestions]
