Returning all water to the spa 100% of the time is not generally the best idea. Your pool water circulation won't be very good if all of your water is coming from the spillover. Typically you use a mixture of spillover and regular pool returns on an automatic sequence from the control system.
Regardless, spillover mode can be setup from the iAquaLink, so you could use it as you describe if you want to. If you don't see spillover mode, there is a dip switch you need to set to enable spillover mode.
The Zodiac G3 cleaner is a suction side cleaner, so it doesn't care where the water is returning.
I an trying to do this..........i want to suck from the Pool and partly return to spa approx 25% for the spillover, manually is easy ....but how
do i do this with the newly installed jandy actuators????