Act 2, Scene 3 Questions

Shakespeare may have included the porter scene for two reasons.

Macbeth and Macduff have contrasting ways of speaking. When Malcolm and Donalbain ask what happened, Macbeth's speech is fake, wordy and even violent, while Macduff is straight forward. For example, when Malcolm and Donalbail ask what happened,

 
One highly ironic incident from Act 2, scene 3 occurs when

Macbeth seems to have changed in this scene. Earlier..... but now...