The first line mentions madness; this is both foreshadowing (that the character will be crazy) and mystery (what will he do?). Foreshadowing is also seen in the sharp senses.

The dilemma is once he's hidden the body, the police investigate, raising the question of, will they find the body?

Reversal is a bit harder, but the very thing that he thinks will protect him (hiding the body) leads him to reveal himself. Lines like this: "If still you think me mad, you will think so no longer when I describe the wise precautions I took for the concealment of the body" show a kind of reversal. Hiding the body is intended to be wise, but is not.