The Cessna 172M inadvertently entered a spin during recovery from a practice power-off stall, with 30 degrees of flaps deployed. The pilot stated that during the recovery of the practice stall he applied, "full power and nose level...the airplane went sideways and started spinning downwards." The pilot did not immediately reduce power, and the airplane's speed increased as it descended. He reported that upon recovering from the spin, the airspeed was over 120 knots; however, the airplane's maximum airspeed with flaps extended was 85 knots. The pilot subsequently retracted the flaps and heard a "creaking noise." Post accident inspection of the airplane revealed that the wings and flaps were substantially damaged.