1. Data science major and units are only introduced in 2018. Chances are, if something is new, it's going to be a little shaky at first.
2. With B. Adv Computing/B. Sci, you're considering a data science major and a computational data science major, right? I don't know the specific difference between the two majors, but they sound awfully similar. I would recommend your second major to be something different, rather than to overlap with your first major, because otherwise you're kind of using the time and effort of two majors to study more or less the same thing. You're interested in maths/statistics/financial maths and statistics, right? Maybe try one of those as your second majors. Computer science is also a decent option.
3. For first year, with data science, the main requirement is for you to take maths. Specifically, MATH1X21 (sem 1), MATH1X02 (sem 1) and MATH1X31 (sem 2). In addition, need to do the new DATA1001 (sem 1/2) and DATA1002 (sem 2) units. Instead of DATA1001, you can take MATH1X05 (sem 2), which is the traditional introductory statistics unit. Instead of DATA1002, you can take INFO1903 Informatics (sem 1), if you're interested in a bit of computer science.
It should be noted that in doing the units above, you're also completing the first year requirement for maths, statistics and financial maths and statistics majors. You can fill up the rest of your first year units in any way you like, e.g. more maths and computer science if you're interested in those subjects, or the other sciences, or HPSC1000 Bioethics (which is a fun and interesting applied philosophy course that is under the faculty of science, and has no final exam).
