I am not sure I follow you. He's trying to use the iTouch as a substitiute for the white Apple remote to control the imac but can't get it into full screen mode by using the iTouch remote. Is this possible?
Is it possible to use the iTouch to launch and control Front Row?
The purpose of the iTouch/iPhone running Remote is to have full control of a remote music library with no access to a monitor (eg. Airport Express, Apple TV with no monitor, etc). It is not a replacement for the little white Apple remote unit to control Front Row, nor can it do so.
Consider it the equivalent of a Squeezebox Duet remote controller.