Your original question asked more than one question, so I have had to edit it down to focus on the climax of this terrifying story. Let us remember that the climax of the story comes after the rising action, where the story reaches its high point, or the stage at which the reader is most engaged and excited about what is happening. It comes before the resolution, when the conflict is resolved and we are given our ending.
It is clear then that in this story, the climax actually comes when the policemen come to visit, alerted by a neighbour about the shriek that was heard as the narrator killed the old man. Interestingly, at first, the narrator is completely nonchalant about their arrival:
I smiled - for what had I to fear? I bade the gentlemen welcome. The shriek, I said, was my own in a dream. The old man, I mentioned, was absent in the country. I took my visitors all over the house. I bade them search - search well.
The narrator clearly feels that he has nothing to be worried about, having concealed the body. He talks of the "wild audacity of my perfect triumph" as he revels in the fact that the policemen sit in the same room where he has concealed the corpse. The policemen are obviously satisfied, but stay talking to the narrator, until he begins to hear a sound, which with terror he realises is the sound of the old man's heart, still beating.
It is this point that is the climax, as the sound of the heart becomes ever louder, driving the narrator insane and causing him to confess to the murder that he would have otherwise gotten away with.
Thanks this really helped me
*climax: the climax is the result of the crisis. it is the high point of the story for the reader. frequently, it is the moment of the highest interest and greatest emotion. the point at which the outcome of the conflict can be predicted.
*resolution: (denoument): rounds out and concludes the action
*rising action: a series of events that builds from the conflict. it begins with the inciting force and ends with the climax .
hope that's can be helpful .. salam from Tunisia