All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
Hopefully, this person will have a good fate, Allaah willing. He had a good ending of life; all praise be to Allaah. The fact that Allaah, The Exalted, has guided him to repentance and ushered him into His obedience serves as a good sign. As long as he had done his best to make up for the missed prayers before his death, then the fact that he could not make up for all of them is pardoned, and there is no harm in that.
There is also no harm that he did not make up for these missed prayers in the correct order; many scholars held that it is not obligatory to make up for the missed prayers in order. We implore Allaah to bestow His mercy and forgiveness on this person, and you should all strive in supplicating Allaah in his favor, for he had a good final stage of life, all praise be to Allaah.
Allaah knows best.