Pesachim 42: When in Doubt, Do or Do Without?

Finishing chapter 2... An interpretation of a very common phrase in the Torah. Also: kneading dough with water that must be "rested" water. And making sure that the dough (and the water used to do so) does not warm up, and risk leavening faster. Noting that not all cases are the same, and parameters for one case do not necessarily apply to another. Is the default permitted unless there's a prohibition, or is it prohibited unless permitted? Plus a list of foods that are simply prohibited on Pesach, from the first mishnah in the new chapter.