With due respect to your position as "Rep", there are some crucial errors here:-
a] Step 2: The mitral valve is ITSELF an atrioventricular valve [between the left atrium and L ventricle], the other A-V valve being the triscuspid valve between the right atrium and R ventricle. Therefore when you say "The atrioventricular valve is OPEN and the mitral valve is CLOSED", this is a self-contradiction.
b] Step 1: The pulmonary valve lies at the opening of the pulmonary ARTERY from the right ventricle - hence, it has nothing to do with the left atrium, into which the pulmonary VEINS drain [bringing blood from the lungs].
c] Stage 3: Once again there is confusion between atrioventricular valve and mitral valve [the A-V valve on the left side of the heart IS THE MITRAL VALVE!!
d] Stage 4: You appear to be confusing the mitral valve with the aortic valve here - if as you say "the mitral valve to open" then blood would be forced back into the left atrium from the L ventricle [this ONLY OCCURS in a patient with mitral regurgitation - HERE WE ARE REFERRING TO A NORMAL HEART!!
Sorry to have to say this, but your username is a misnomer.