We have total of 6 subjects including one Optional Subject. The 5 compulsory subjects are : Math, English, Physics, Chemistry, ICT. Optional Subjects are Biology and Statistics. One can select any from those 2.
I would say that this does not hurt you because you're school doesn't offer them. Taking the most advanced courses in your school is what colleges want to see. You could even look into taking some classes at a local community college or trying out some MOOC's such as edX and coursera if you're interested. You should be fine if you are taking the most that your school offers.
No! Colleges can see what your school offers, so they do not expect you to take classes that your school does not offer. They simply want to see that you are challenging yourself so if you have honors classes it would be advisable to take those!
I would tend to say that it depends on what kind of universities you'd like to go. For schools ranked behind 30th it would not make much difference given your circumstances, if you have a great GPA. However, for a top school AP is kind of basic requirement. Self-learning AP is not that hard. You only need a Barron's AP book to get a 5.
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I've taken online courses that are related to the major I want to take which is Computer Science. Should I add these informations in the application too?