The requirement for eruv chatzerot to be set up before bein hashmashot- application to Erev Pesach that falls on Shabbat- should the eruv be made of chametz or matzah?
Joint eruv partnerships where one party forgets to contribute- does this nullify the partnership retroactively? Application to making berachot on behalf of another and making a mistake
The law of eruv for a student at the Rebbe's house- application to guests staying at a hotel, in a communal dining room, and scenario of hotel owner being Jewish
The halacha of renouncing domain rights on Shabbat- application to one who forgot to be mevatel/nullify befors the onset of the 6th hour on Erev Pesach