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.
Just thought Kiwix seems like it’ll be handy here, it lets you download Wikipedia and some other websites, and they have an Android app to view them.
(They have a web version too, which I actually selfhost for if the world ends or something /s)