yes you do!
to go to secret island you need to get a ticket but they are kind of hard to get
Well, When you reach the farther game there will be a man who gives you a secret code for a secret exit.
A coconut bone and secret ingredient
On cinnabar island but you need to get the secret key in Pokemon mansion first.
It is in the secret store room behind the filing cabinet in the detention room on Big Nate Island. You need the blue prints from Nate's locker in order to access the secret room.
You walk up to the mountain to go to Secret Island in Sootopolis by using 114. You will smash rocks and defeat trainers along the way. You need to find the passageway to Meteor Falls.
You need to click on the file cabenet and then go down the ladder.
You need the secret key which is found in Pokemon mansion which is also on cinnibar island.
you need an action replay,next type the run anywhere code, after that go to fullmoon island and put the marking map then go to the secret islands.
Go to Pallet Town and Surf down, and you will get to Cinnibar Island. You need to get the secret key from the pokemon mansion on Cinnibar Island to get into the gym.
You will need to use the Secret Key which is hidden in the basement of Pokemon Mansion which is located on Cinnibar Island.
An old bone, (inside cave) The secret ingredient, (also in the cave) and carbonated coconut milk.