MC pretended to be younger than she actually is to infiltrate her adoptive (actually biological) family. At the very end of the story her family finds out about her original identity (they all accept her)
MC regressed retaining his actual older body (his self of this timeline exists as a separate entity). He eventually confesses to his adoptive father that him and his younger self are the same person and about his regression
MC confesses to his parents about his previous life. His father accepts him but I remember dropping the novel a lot of years ago due to his mother acting like a b- (due to this reason and other events)
FL and ML both regressed, so they obviously talk about their experience
FL confesses to her family (father + 3 brothers) that she's not really og!fl: the brothers accept her without problems, the dad eventually accepts her after a lot of drama. The ML knew since the beginning.
ML can see the end (death) of each individual he comes across, so he saw FL's deaths from her previous lives since the beginning
FL's parents realize that she's their future daughter that went back in time
Messages