as for the dream, I would say the one where they ran away was the dream(or theoretically the loop before the story we saw unfold. Based on the fact that it seems he dies after his years are up in a peaceful manner and Mikasa looks closer to her look from before instead of her short boyish look that she has now, especially if you compare the runaway version of her to how she looked in his “dream” in chapter 1
edit: went to look back, the “see you later” scene at the end of the chapter is literally the dream from a different PoV
I just don’t know how she remembered the previous loop
also could you please add a spoiler tag to avoid ruining it for new readers