Kavod HaRav: Can I be Motzei the two loaves and say Birkat HaMazon on egg matzah on Shabbat / Erev Pesach? What happens if I ate pita bread and had leftovers?

Shalom U'vracha, 1. Sephardim who go by the (Shulchan Aruch) eat egg matzah (matzah ashira) on Pesach and definitely on Erev Pesach. (some Sephardim don't eat egg matzah because they are afraid that water is added to it in the factories and may cause it to become chametz). Ashkenazim don't eat egg matzah on Pesach. According to the Aruch Hashulchan (145,5), Ashkenazim may eat egg matzah on erev pesach (but make a hamotzi blessing on it and birkat hamazon only if one eats four egg volumes (kebaitzim) of the egg matzah bread and eats a satisfying meal with it). According to the Mishnah Brurah and Igrot Moshe, Ashkenazim don't eat egg matzah on Erev Pesach after the fourth hour of the day (around 10:10am this year). There are different ways to solve the problem of seuda shlishit: you can eat kenaidlach or even fruit or meat. Some people have the minhag of splitting the morning seudah into two with a little break in the middle. 2. If you have leftovers of bread you can gather it and flush it down the toilet, or throw it into the public garbage. (some say that you must pour soap or economica on it beforehand; but it is not mandatory).