What happens if the pilot tries to do a loop in a full-motion simulator?
The motion systems in simulators do NOT mimic the airplane's attitude. Whether the airplane is right-way-up, upside-down or inside-out has no effect on the motion system.

The motion system is used to move local gravity around to mimic the accelerations felt while flying. eg. To mimic the braking during landing, the cab tilts forward, moving local gravity forward relative to the cab, making it feel like you're hanging in the straps due to the braking. Note that when you are braking during landing, the cockpit is level, and yet you are still propelled forward.