wasted a lot of my school years. Is it still possible to get into a top university?

I feel like I was asleep for most of my journey through school.

I wasn't a terrible student, but I wasn't an exceptional one either. I was somewhere in the middle, and honestly, I didn't take my education as seriously as I should have.

I'm 20 now, and I still haven't gone to college. Part of that is because I didn't want to settle just for the sake of getting a degree. If I'm going to spend years studying, I want to aim for a genuinely great university.

The last year was especially difficult. I went through almost a year of depression, and I lost a lot of time because of it. I'm not proud of that period, but I also don't want to lie to myself about what happened.

The important thing is that I feel awake again.

Since last year, I've started learning programming seriously again. Instead of only watching tutorials, I've been trying to actually build projects. I also completed an internship at a local company, which gave me some real-world experience.

Now I want to make up for the time I lost.

I'm willing to put in several years if necessary. I want to build a strong academic and technical profile and do everything realistically possible to increase my chances of getting into a genuinely excellent university.

There's another difficulty: I'm an international student, not from the US, so I know admissions can be even more competitive and complicated for someone in my situation.

I'm not necessarily only interested in the US either. I'd be happy to study at an excellent university in Europe, Asia, or elsewhere. My main goal is to get into a truly strong university, especially for Computer Science, where I can surround myself with ambitious people and have strong opportunities afterward.

So, if you were in my position, what would you do over the next 1–3 years?

What would actually make the biggest difference for someone with an average high-school record but a strong upward trajectory?

For example:

How important are standardized tests like the SAT?

Should I focus heavily on competitive programming / Olympiads?

Are research projects realistic for someone starting late?

How valuable are internships and serious personal projects?

Should I try to build something significant, such as an open-source project or startup?

Would taking 1–3 gap years hurt me, or could I use them to build a much stronger application?

Are there universities outside the US where this kind of comeback story can realistically be competitive?

I know that getting into places like MIT, Stanford, Oxford, etc. is extremely difficult, especially as an international applicant. I'm not looking for false reassurance.

I want an honest answer:

Given my starting point, what would you do if the goal was to maximize the probability of getting into a genuinely top university? wasted a lot of my school years. Is it still possible to get into a top university?