Does receiving the deferred mahr only apply if the husband initiates the divorce?

If you've taken the Nikah Masterclass you'll understand that there's a difference between talaaq and khula.

Talaaq is the initiation of the divorce process by the man. Khula is the initiation of the divorce process by the woman. They both have certain rights and responsibilities during that time. If the man initiates divorce, he has the right to take the woman back during the iddah period but he also has the responsibility to support her financially during the iddah period.

And the woman, if she initiates the khula, then she has the right to be maintained as a wife during the iddah period, but she has the responsibility to return the mahr, or part thereof, to her husband.

So if you have a mu'akhr, that mu'akhr is not going to be paid to you. Essentially, you would do one of two things.

You would either say, look, just give me the khula that I want. I don't want to be married with you anymore. And therefore, instead of asking for anything or giving anything back, I will simply walk away and you won't have to pay the mu'akhr.

Or the man might say, no, I want both the muqadam and the mu'akhr back.

And you would be expected to pay back the portion that he had paid you up until that time.