In act 3 discuss: the rewards that Mcbeth and Lady Macbeth get, the change, the subsequent murders &they have to pay for their murderous actions
Your question about Act 3 of Shakespeare's Macbeth is vague and a bit broad, and it covers too much territory for this Q & A format. It involves four questions instead of the one allowed. Also, any consequences the Macbeths suffer don't come in Act 3. I suggest you break your questions up into parts and ask each one separately, and be as specific as possible. We can give you far better answers that contain far more information if you do so.
That said, Macbeth is crowned king by the time the play reaches Act 3, so that is their reward, I guess. Macbeth also orders the killings of Banquo and Fleance in Act 3, but Lady Macbeth doesn't have anything to do with it. That may be the change you ask about, as well. Lady Macbeth is shut out of the decision-making process by her husband, and he takes over the planning.
And this is probably a mistake on Macbeth's part. Lady Macbeth planned a near-perfect murder of Duncan. Had Macbeth stuck to her plan, they may have gotten away with the murder. But he veers from the plan by killing the grooms, which casts suspicion on him. He then shuts his wife out of the decision-making process, and orders the killings of Banquo and Fleance, which further leads to suspicions about Macbeth's treachery.