Please, if you have a link to my previous AP Physics 1: Simple Harmonic Motion Review, please update that link.
FYI: The mistake was, in the words of Mario Penaloza, whom I thank both for noticing and letting me know about the mistake, "If position #1 is already to the right then the graph you showed for velocity is wrong because the derivative of cos(x) (position) is -sin(x) not sin(x) … Let me know if I'm wrong.” That’s correct, I forgot a negative sign, that is all it was. However, it made the velocity graph incorrect, which is unacceptable.