I can think of a few things I do not like about the world today that I imagine I could improve in a scenario like that. They include:

• Much of the world's communication is mediated through centralized social media platforms that use opaque algorithms to determine what content people see. (Yes, this is a very Lemming concern)
• There is a significant rise in (mostly) right-wing populism worldwide, driven, I think in part by the above.
• Corporations and governments are increasingly able (and motivated) to block access to their digital systems from general-purpose computers that their owners fully control. Even the mainstream press saw Microsoft Palladium as a nightmarish power grab in 2002, but did not react the same way to Google SafetyNet in 2014.
• I do not own a Gordan Murray Automotive T.50.

Social media

2002 is before anybody had a convincing lead in this field, but blogs were already popular, and on the Internet, nobody knows you're a ~~dog~~ kid. I could start planting the seeds of more advanced federation capabilities through open source development right away. I'm assuming I have a computer of course, but I think even if I didn't I could probably get my hands on something older just by expressing interest and aptitude.

After laying the technical foundations and establishing some credibility as a developer and technologist, my goal would be to build something with significant mainstream appeal by the time Facebook opens to the public in late 2006. I'd need access to money at that point, whether my own or through investors, though as a federated system, I wouldn't have to bear all of the costs (nor would I have the ability to extract all the profits, but even a hundredth of Zuck's net worth is obscenely wealthy).

Populism

I honestly do not know how much of this is due to the present day social media environment, but I'm sure it's a significant factor. I like to think that by tuning the design of social communication tools for more thoughtful discussion, more thoughtful leaders would thrive. Barring that, if I was obscenely wealthy, I could put my thumb on the scale by less honorable means, and I like to think I wouldn't be so terribly corrupted by the money and power as to use it for evil.

One idea that comes to mind for political discussion is used in Pol.is and (perhaps ineffectively) Twitter community notes: surface points where people who usually disagree are in agreement.

Protecting general purpose computing

This one is hard to the point I'm not sure it's achievable, but It's so important. The obvious approach is to launch a mobile operating system, which would have to at least stay even with Android. Microsoft tried this in 2012, and that was too late despite their entry attracting some diehard fans. If I have the superior OS and majority market share, I'm in a good position to resist attempts to mandate locked bootloaders and remote attestation.

The good news is it's not hard to do a better job with some fundamental design decisions given perfect hindsight, and with Android being open source, it wouldn't be hard to support Android apps. There weren't a lot of dependencies on Google's services in the early days.

This one would be reliant on the social media play for capital and credibility. It would need to be well underway by 2010, which is a tight timeline, but not impossible.

An absurdly expensive sports car

If either of the above plays works even moderately well, I can have my 11,500 RPM redline V12 three-seater. If not, I'd still be in a position to make a bunch of money, and I'd be trying some of them in parallel.

Nobody's going to give a ten year old control of an investment account just because they say they have some good ideas about the stock market, but if my hypothetical parents are anything like my real ones, after a couple months of demonstrating nearly-unbelievable skill at investing fake money, I'd be able to talk them into letting me invest a couple hundred dollars of real money and snowball things from there. I'd also know which startup ideas worked, what decisions were important in their success, and which founders I wouldn't feel bad about ripping off.

Even as reality diverges, I think certain trends were inevitable. Social media will happen. Smartphones will happen. Streaming will happen. EVs will happen. Generative AI will probably happen, but I think I might try to push that one back a few years if I was in a position to do so. Flying cars, fusion power, and space colonies probably aren't happening by 2025 regardless of how many butterflies flap their wings.