Is there a possibility that I may get rejected

Yes, there is a possibility you will get rejected, if only because the universities you're mentioning reject 90-95% of the students that apply to them. I can't really tell what your expectations are from the way that you worded your question, but no one, no matter how strong a student or how good their academics are, should really expect to get into many of these schools, much less all of them. The best students will apply to 10 of these kinds of schools and get into maybe 2 or 3. That's how their admission process works.

More towards your question, colleges will look at international students based on the systems in the country they're coming out of, so doing well on your A levels would be roughly equivalent to doing well in AP classes in an American curriculum. Now, to be clear, essays aren't really for "saving" people, because top universities will typically have cutoffs for things like SAT score and general grades. They almost never admit anyone who falls below those cutoffs, whereas above those cutoffs essays become extremely important in differentiating between similarly accomplished students. What I would do is compare your general accomplishments to people from your school or area who have gotten into these schools in the past—that's the best gauge you can get for how your process might turn out.