Did Minato make a deal with the death god?
No, he tricked the death god into thinking he was taking his soul. Instead he sealed his soul within Naruto.
Yes, in exchange for his heavenly soul the death god granted him access to Naruto's body when the 9th tail is about to be released.
No deal was made. He simply made the seal so he could escape the death god when the 9th tail is about to be released.
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