Assume that the future can change based on your actions, so any historical information that you bring along with you from the intervening 25 years may quickly drift out of the new realities history.
Edit: also assume that you can be given a healthy 21-year-old body if you want or take your previous self’s place.
Further, identification will be provided for you if you were not born at that time.
Like the other person mentioned their family, I would say that about my friends and other relations. I don’t think it’s possible for me to redo my life in a way that my decade old friendships would be the same (or even better) than what they became. I don’t even know if I will feel the same about my friends if I decide to relive my life as memory is a precarious thing and I can’t rely on how I feel about them to last until I meet them again and live life interacting with them while trying to change the world.
I could consider a 21yo body but as a millennial I would end up overaged for the people who were important in my life to have any meaningful relation with them.
I have considered the scenario of reliving my life, correcting my mistakes and maybe making some massive changes along the way, if I could somehow guarantee keeping the things that matter to me the same.