How to Get Through the Rocket's Hideout in the Casino

1). Press the button behind the poster in the rear of the casino. This will open a secret door in the northeast corner of the room. Descend the stairs to enter the first basement floor.
2). Descend stairs until you arrive at the third basement floor.
3). Navigate through the maze in the third basement floor. The maze features spin tiles that will send you spinning in a single direction until you hit an obstacle. Experiment with these spin tiles until you reach the stairs in the southeast corner of the basement. The stairs will lead you to the fourth basement floor.
4). Defeat the Team Rocket member in the northwest corner of the room. He will give you the Lift Key item.
5). Ascend the stairs until you return to the second basement floor.
6). Navigate through the spin tile maze on the second basement floor. The room at the end of the maze, which is in the southeast corner of the floor, contains an elevator.
7). Enter the elevator and ride it to the fourth basement floor.
8). Walk north and defeat the two Team Rocket guards.
9). Enter the next office and battle Giovanni. His Onix and Rhyhorn are weak to Fighting-, Ground-, Steel-, Ice-, Grass- and Water-type attacks; however, his Kangaskhan is only weak to Fighting-type moves.