If you were to ABRUPTLY apply full flap whilst maintaining the same pitch attitude, YES, the aircraft will stall. (You'll need some good degree of remaining elevator authority to achieve this).
Stalling a 'Clean' wing and a 'Flapped' wing will be at approximately the same angle of attack, hence, with Flap applied, the Pitch Attitude at the stall will be LOWER.
Regards,
Old Smokey