The MiG-29 and Su-27 can’t truly maneuver post stall. But their control surfaces and overall aerodynamics are designed to behave a certain way even at very high AoA and low airspeeds to specifically allow the maneuvers you named. I.e. while in a cobra, bringing the elevator back to neutral will cause drag at the tail of the aircraft which imparts a torque that will pitch it out of the cobra.