"the subject of a verb in a sentence is the performer of the actions expressed by the verb". is the above statement always true.if not outline the flaws of the question given
No, it's not always true. Of course, in many sentences the subject is the performer (actor), but in passive clauses the subject of the verb is the patient, not the actor.
"The cat chased the mouse". (Active clause: subject = actor)
"The mouse was chased by the cat". (Passive clause: subject = patient)