Can I Hope to Change Everything After My Rebirth?

Will I make the same mistakes again when I return to junior high school? Can I change the future? Or will I go back to the past and say that I have entered a parallel world? Is it a brain in a vat or a big dream? Is it a scam or reality? Is it like becoming a genius in a novel or becoming the richest man through future information? Or is it now possible to walk the same path in the past and live a miserable life again? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.