An online Jewish community I'm fond of has some unanswered questions that came out of Pesach this year. Can you answer any of them, dear readers?

• Why do we designate specific matzot for seder rituals? We break the middle matzah; we eat first from the top one and use the bottom one specifically for the Hillel sandwich. Why? What's the symbolism? (I'm aware of the interpretation that the three matzot symbolize the three "groups" of Jews -- kohein, levi, yisrael -- but that doesn't explain these positional associations.)

• If your house is always kosher for Pesach, do you have to search for chameitz? That is, is the command to search for chameitz, period, or is it to search for any chameitz that might be in your house, and if you know there isn't any you skip it?

• Why does making matzah require specific intent but building a sukkah doesn't? When making matzah (today I learned), it's not enough to follow the rules for production; you have to have the specific intent of making matzah for Pesach, or apparently it doesn't count. This "intent" rule applies to some other commandments too. But it doesn't apply to building a sukkah; you can even use a "found sukkah", something that happens to fulfill all the requirements that you didn't build yourself, to fulfill the obligation. Why the difference?

I tried searching for answers for these but was not successful. I have readers who know way more than I do (and who can read Hebrew sources better than I can). Can you help?