One may not eat matzah on the 14th day of Nissan (i.e. erev Pesach, beginning from the night of the 14th) so that there should be a “heker” (recognition) that the Matzah being eaten at the seder is special, for the Mitzvah of Achilas Matzah. Some have the custom to refrain from eating Matzah from Rosh Chodesh Nissan, while others are even more stringent, and do not eat Matzah beginning 30 days before Pesach (i.e. from Purim). {See Shulchan Aruch w/Mishnah Brurah 471:2, Igros Moshe OC1:155, Rav Poalim 3:27.}
There is a Mitzvah for every Jew to study Hilchos Pesach beginning thirty days before the Yom Tov (i.e. on Purim) to know the correct way to perform the Pesach mitzvos. This obligation extends throughout all the days of Pesach itself. Included in this Mitzvah is the Shabbos Hagadol Drasha, a portion of which should be devoted to Hilchos Pesach. {Shulchan Aruch w/Mishnah Brurah 429:1.}{[email protected]/Matzav.com Newscenter}
