At the risk of beating this very dead horse even further, I'd like to point out two things that this OP has said.
"If the final determination was 9/25/2012 + 3 years = already past?The 3 years, would be up now correct? If the final determination was 9/25/2012 + 3 years = already past?"
And in the very first post, he said, "About three months ago, I got ......." Three months ago, about the time that three years would probably have been up.
It is entirely possible that the reason that this collection effort was reopened is that there is a tickler placed by the collections system on each overpayment case, so that it doesn't slip past the three year deadline without any collection efforts being put into place to extend it. They are really really doing everything they can to produce revenue in that state right now. I would not take a chance on any of our best guesses here about what "requiring restitution" means to the Michigan system. I'd work with them to the best of my abilities. I suspect you have tried to be a little devious and at least avoidant with them in the past.
If you are set up on a repayment plan and you miss a payment, or move or try to default for any reason, they have every right to come after you even though they have set you up on a payment plan. The plan does not protect you from further collection efforts. BTW, please make sure you provide them with very accurate information on your request for a waiver, don't forget to mention any assets or sources of income, because your waiver is the very best hope you have of getting this taken care of.

