Flaps will not extend differently on each side as assymetry protection systems will lock them out, on Classic 747 there is no assymetry protection with the alternate electrical system so it is not a permitted procedure to operate the system after an assymetry trip. One flap drive unit operates inboard flaps while a second operates the outboard so it is possible to have a failure of one system in which case the alternate drive system may be used.The assymetry protection system uses the cockpit flap indicator - split pointers trigger the trip.