You don’t mention your budget. Are you hoping for significant need based aid, or can your family fund these colleges?
Re: your chances at HYPSM and Caltech…it’s impossible to chance an international student for these colleges. The acceptance rate for internationals is low single digits meaning it’s a very high reach for all international students. At these colleges, more than 90% of students do not get accepted, and that %age is even higher for international students. IOW, many many many well qualified international applicants do not get accepted. So…you can apply and see.
It also sounds like you have at least a couple more years of high school left. Could you clarify that?
Regarding the things you haven’t done yet…really…not much can be said about them as you haven’t done them yet. And you have no idea how you will do. That includes the SAT.
What is your country of citizenship? Is it the UK? You need to make sure you have sure things for acceptance in your home country.
I’m very unclear what year you are in high school…please clarify that.
Are you guaranteed an affordable acceptance at any of these colleges?