(1) When do students in Canada learn about the four triangle centres (centers), circumcenter, incenter, orthocenter, and centroid? In the USA (more precisely, Indiana), the math curriculums are by topics and the 9th grade students who completed Algebra 1 can take Geometry in which they learn about them. I looked up some textbooks for Grade 9 to 12 in Canada and couldn't find about them.
(2) How could students in Canada (Ontario) take both MCV4U Calculus and Vectors and MDM4U Math for Data Management in their 12th grade? MHF4U Advanced functions should be taken before MCV4U. MCF3M Functions and applications should be taken before MDM4U. It seems that the 12th graders should take all three MHF4U, MCV4U, and MDM4U in their last year in high school. I think in USA (Indiana) students take Algebra 2 in Grade 10, Precalculus in Grade 11, and both Calculus and Statistics in Grade 12. In Algebra 2 students are introduced to the early part of Precalculus including the essential functions. It seems that MHF4U still covers Precalculus that is offered in the 12th grade at the same time with MCV4U Calculus.