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.
Get every flagship CPU and GPU from 2000 to today that I can get my hands on. Also as much open source code as I can get hold of. And especially AI stuff - there’s several fully open source models, so bring those, and as much technical writings on them as possible.
Speaking of which, download every science paper published since 2000 that I can get hold of, in every possible field.
Get as much info on the 2000 election as possible, to hand to Al Gore, see if he can win that election with a solid unassailable margin.
Research stocks, lottery, and everything else I can to get fast money within the shortest possible period of time after I get there, so I can get super rich before the butterfly effect makes predictions impossible, I need billions in seed money and I need it fast.
Then use that money to start a private research group, and hand them all the scientific papers I brought. Get those experts to work studying all this knowledge and figure out what can be turned into practical technology. Turn some of this into profit-making devices to fund continued development, but release as much as possible for free.
Essentially, deluge the world in as much new technology as possible, mostly free and open source, holding back only as much as necessary in order to fund continued research.
And oh jeez the pharmaceutical industry. Release for free every drug made since 2000, so the pharmaceutical industry can’t get their patents in them.
Big list of stuff there, but if I pulled off even half of it, the world would probably be a much better place in 25 years than in my original timeline.