You need to get action replay codes and have an action replay you cannot get to 8 island on Pokemon fire red. there is no such thing as 8 island . i k what your saying, you have to go to a Nintendo event.
The official name of island 4 on Pokemon FireRed is Floe Island. To access Floe Island you need the Tri-Pass from Bill. To obtain the Tri-Pass you need to have defeated the Gym Leader of Cinnabar Island.