I'm Lost, My study plan is a mess.

Hello there, I'm currently in year 10, O-3, studying towards going abroad, that's my mission, I'm a partially bright student, yet I'm pretty lost, I've been moved around my whole life, From America, to British system schools, to IB, back to British, Now we've "settled" in I go to school, I'm extemped from three subjects, considering my nationality, Urdu, Pak Studies, And Islamiyat, but I have to pick up three or more subjects, I intend to go towards, computer science, yet i'd like to take a side of Buisness, so I have to choose a couple of subjects for those, and the school is preparing us for O levels, but I want to take the IGSCEs, which I'll self study for, but I'm going to need to make my choices and decide quick.

So the main points are these, what will happen after O levels, about the college application, Do I send it after O levels, after A levels, I don't understand, also another part is what is the difference between these two different topics, and will I be able to get into a college?