I don't know if tasks change the more ranks you earn. But if I've been tasked to Boil and I do a recipe that requires Boil and Simmer, does that work? Same way around, if I am tasked with Simmer and do a recipe that requires both, do I earn my rep?

To add to what Gretchen said, tasks do change as you progress in ranks. So as you learn more, you'll have to make more difficult formulas in order to get reps.