Walkthrough
After entering Celadon City, you will notice several Team Rocket Members within the city. By going to the Game Corner, you will find Jessie and James playing on some of the slot machines within it. The two will be discussing the Rocket Hideout, explaining to each other how to access it. By going to the Team Rocket Grunt in the back of the Game Corner and defeating him in battle, you will be able to access the Rocket Hideout by interacting with the poster he was guarding.
Once inside the Rocket Hideout, you will have to battle waves of Team Rocket Members while trying to navigate through the tile puzzle mazes found throughout it. Your goal will be to find the Team Rocket Grunt that has hold of the Lift Key, an item that will grant you access to the elevator so you can reach an area on the bottom floor. This Team Rocket Member will be found on Basement Floor 4, and after they are defeated, they will actually throw the Lift Key onto the railing over the wall. You will then gain control of your Starter Partner Pokemon in order to complete a puzzle through the air vents and obtain the Lift Key.
Only after obtaining the Lift Key will you be able to use the elevator found within the Rocket Hideout. But be prepared, as three more difficult battles will lie ahead of the elevator on the bottom level.
Trainers
Game Corner Entrance:
Team Rocket Grunt: Level 29 Raticate
Basement Floor 1:
Team Rocket Grunt: Level 29 Golbat
Team Rocket Grunt: Level 29 Koffing, Level 29 Rattata, Level 29 Rattata
Team Rocket Grunt: Level 29 Voltorb
Team Rocket Grunt: Level 29 Ekans, Level 29 Arbok
Basement Floor 2:
Team Rocket Grunt: Level 29 Hypno
Basement Floor 3:
Team Rocket Grunt: Level 29 Golbat
Team Rocket Grunt: Level 29 Rattata, Level 29 Voltorb
Basement Floor 4:
Team Rocket Grunt: Level 29 Grimer
Obtainable Items
Basement Floor 1:
Ultra Balls: Western Office
Mighty Candies: Under Desk In Southeast Office
Hyper Potion: Southwest Main Office (Accessed Through Basement Floor 2)
Great Ball: Southwest Main Office (Accessed Through Basement Floor 2)
Basement Floor 2:
Nugget: Northern Tile Puzzle
Awakening: Western Tile Puzzle
TM05: Middle Tile Puzzle
PP Up: Southwest Tile Puzzle
Basement Floor 3:
TM20: Eastern Section
Guard Spec.: Hidden In Front Of Poke Ball Machine In Eastern Section
Revive: Northwest Section
X Speed: Western Tile Puzzle
Rare Candy: Eastern Tile Puzzle
Basement Floor 4:
PP Up: Near Boxes By Stairs
Hyper Potion: Near Boxes By Stairs
Lift Key: On Railings Above Wall (Starter Partner Pokemon)
Elixir: Southwest Corner (Accessed By Elevator)
Silph Scope: Defeat Giovanni
Post Game
Walkthrough
After defeating the Elite Four and starting the Master Trainers Challenge, you will find a number of Master Trainers within the Rocket Hideout. In total, there will be four Master Trainers to defeat.
Trainers
Basement Floor 1:
Scientist Adam (Master Trainer): Level 75 Arbok
Basement Floor 2:
Hiker Eugine (Master Trainer): Level 75 Rhydon
Basement Floor 3:
Scientist Donnie (Master Trainer): Level 75 Weezing
Basement Floor 4:
Youngster Shawn (Master Trainer): Level 75 Persian