the battle of the department of mysteries

what happens if harry knew everything before hand. what if he knew in the department of mysteries. what if he jumped through the veil after knowing more pain and torture was to come what if he couldn't do this life anymore.
to suddenly wake up in a different body. a different world. he was still harry potter but he had sirius again. and his parents were alive. they never died on that fatal Christmas. except remus is alive and well despite definitely being the age of post war.
join harry as he discovers this new life.