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.
A healthy 21 body and 1999? Fuck taking over the world, and I don’t need your stinking backpack, just tell me where to get that ticket and where to show up, I’m not going to miss this! I’m taking a cyanide pill though when 2020 rolls around; I’m not doing this shit again.