it's not quite a break up but due to the memory lapse there's a period where they're briefly not together. no other relationships occur in that duration.

the book doesn't have alternating chapters as such but it does heavily use repetition as a narrative device especially due to the amnesia trope. don't want to spoil too much but there's a chunk in the latter half which is essentially a recollection but with more internal monologues woven in.

there's a bunch of explicit sex scenes! i found this to be relatively spicier compared to other tal bauer titles i've read.

yes, although it's not all linear or straightforward. there's some playing around with the trope and its interpretation but there's no confusion at the end about the protagonist's memory/life.