But he isn’t the original Snape anymore so his furute version should have changed to the one with this one’s personality right. Correct me if i am wrong just a little confused.
This is only if we adopt the thinking that there're a singular timeline, but Vader existence already contradict said theory, so it's plausible to say that there are multiple lines of reality that diverge from each other at a certain point, so yeah even if current Severus isn't the same as their Snape it doesn't mean their previous reality would have changed, at most they've gone to a parallel world
Well! this is where I stop, absolutely useless plot. With Vader in Snape’s body the future was already going to be changed. The fact that Granger takes the name of Prince, a name that Sev knew and pretends to be a sister, tut tut, useless as a plot. Hermione is a know-it-all. There’s no way Vader-Snape likes her.