(1) Good point. The Yerushalmi does seem to be arguing with the Bavli, at least according to Tosfos and the Rashbam's explanation of the Gemara in Pesachim, who say that "b'Bas Achas" means one after the other, as the "b'Krach Echad" means here in Shekalim.

However, according to Rashi's explanation in Pesachim, that "b'Bas Achas" means that one poured all four cups into one cup and drank it like that, the two Gemaras are not necessarily arguing. The Gemara in Pesachim is referring to when all four cups were consumed at one time from one large cup, in which case Rav says one does not fulfill his obligation of Arba Kosos, while the Gemara in Shekalim is referring to when one drank each cup separately, but did not pause in between each cup, in which case the Gemara says that one fulfills his obligation. (YEFEH EINAYIM to Pesachim 108b, and the SHEYAREI KORBAN to Shekalim 13a (according to the pages in the Yerushalmi printing).)

(2) The KORBAN HA'EDAH says simply that it was the Minhag in the times of the Gemara to recite Hallel in Shul on Pesach night, as a Zecher for what was done in the Beis ha'Mikdash, where they recited Hallel when they prepared the Korban Pesach in the Beis ha'Mikdash (as the Mishnah says in Pesachim 95a).

The IKVEI AHARON explains that even though they also recited Hallel when they ate the Korban Pesach (as we do at the Seder), as the Mishnah in Pesachim says, nevertheless the Hallel recited upon preparing the Korban was said in a large Chaburah of at least 30 people, as the Rambam writes (Hilchos Korban Pesach 1:9). Thus, the preparation of the Korban requires a Tzibur, while the eating of the Korban can be done even by a single individual by himself. Therefore, the recitation of Hallel in the Shul, when there is a Tzibur, is commemorative of the Hallel recited upon the preparation of the Pesach.

(3) Good question, especially in light of what we wrote above in the name of the Ikvei Aharon explaining the Korban ha'Edah. Hallel was said twice in the times of the Beis ha'Mikdash -- once when preparing the Korban Pesach and once when eating it. Perhaps it refers to someone who does not have the Minhag to say Hallel in Shul, in which case he fulfills his obligation to say Hallel at home when he hears it at Shul. (See Pesachim 86a, where we learned that one may say the Hallel in a different place than where he eats. This is no proof, though, because the Gemara here is talking about saying Hallel at a different time .)

-Yisrael

You are correct -- the Hallel in Shul seems not to have any connection to one's Sipur Yetzi'as Mitzrayim at home. (This was what I was referring to when I wrote, at the end of the answer, that the comparison with the case on Pesachim 86a is not accurate. In that case, the people had already done Sipur Yetzi'as Mitzrayim, and they just moved to another place to recite Hallel. In this case, though, the person who hears Hallel in Shul has not yet performed Sipur Yetzi'as Mitzrayim! If so, that Hallel should not qualify as the Hallel which must be said upon the Sipur Yetzi'as Mitzrayim, which is exactly what you are asking.)

It must be that Rashi holds that the Yerushalmi in Shekalim and the Bavli in Pesachim are arguing. The Bavli maintains that Hallel must be recited with the Matzah present, and the Hallel said in Shul does not suffice to fulfill one's obligation for the Hallel that must be recited when Matzah is present. The Yerushalmi holds that there is no need to recite Hallel while Matzah is present.

(This answer has two problems. First, the Korban ha'Edah's explanation, according to the Ikvei Aharon, is difficult, because he says that even according to the Yerushalmi, there is a Din to say Hallel in Shul, commemorative of the Hallel said at Shechitas ha'Pesach, and a Din to say Hallel at home, commemorative of the Hallel said at Achilas ha'Pesach. How can the Hallel being said at Shul cover the Hallel of Achilas ha'Pesach -- before anything was eaten! To answer this point, it could be that the Korban ha'Edah does not mean to say what the Ikvei Aharon reads into his words. Perhaps the Korban ha'Edah is not saying that the Yerushalmi holds that there are two types of Hallel said on the night of Pesach, but that the Yerushalmi indeed argues with the Bavli and holds that there is no Inyan to say Hallel at the meal over Sipur Yetzi'as Mitzrayim, or commemorative of Achilas ha'Pesach. Perhaps if you have the opportunity, you can bring this issue up with the author of Ikvei Aharon himself, Rav Yaakov Wehl (5013-15th Ave., Brooklyn, tel. 718-851-9199).

Second, the Gemara itself in Pesachim 85b-86a says that they went up to the roofs to recite Hallel. But it mentions nothing about taking their Matzos with them!)

To answer your question from Rashi, it seems that the element of Matzah being "Lechem sh'Onim Alav Devarim Harbeh" is merely l'Chatchilah, and is not Me'akev. The Yerushalmi is discussing a b'Di'eved case (that is, if a person drank the four cups without pausing between them; this is b'Di'eved because the Mishnah in Pesachim (117b) says explicitly that l'Chatchilah one finishes Hallel upon the fourth cup).

Yisrael Shaw