(1) I am not sure which Mishnah you are referring to in this question so please can you tell me?

(2) (a) The Mishnah 19a states that if someone who lives in a non-walled city (where the Megilah is read on 14 Adar) went to a walled city(where Megilah is read on 15 Adar) or vice versa, if he is going to return to his home town then he reads the Megilah on the same day as his home town.

Rava explains that when the Mishnah says that the person who lives in a walled city and went to a non-walled city nevertheless reads on 15 Adar, this is referring to a scenario where he is going to return home on the night of the 14th (Rashi DH Ella explains that he will leave the non-walled city before daybreak on 14th) but if he will be in the non-walled city for the entire night of 14th Adar then he reads the Megilah on 14th together with the dwellers of the non-walled city.

(b) So the critical factor is whether the visitor will be in his host town for the entire night on which they read the Megilah in the host town.

(c)The reason for this is because a person is considered to belong to his host town (for the purpose of reading the Megilah) even though he is in the host town merely for the day of the reading of the Megilah. This Halachah is derived from the verse in Esther 9:19 "who dwell in the non-walled cities". This would appear to be superfluous because the verse already discussed the "Jews of the walled cities". We therefore learn from this that someone who only dwells in a non-walled city for the day is also considered a dweller. It is only if he will not be there in the daytime at all that he is not considered as a dweller.

(3) The Mishnah (above 2a) states that cities which were surrounded by walls in the time of Yehoshua the son of Nun celebrate Shushan Purim. The Ran (1a in Rif pages DH v'Yesh) explains that the reason it depends on Yehoshua is in order to pay honor to the land of Israel which was desolate at the time the miracle of Purim took place. If the guideline would have been whether the city possessed a wall at the time of Achashverosh then no city in Eretz Yisrael would celebrate Shushan Purim but in contrast at the time of Yehoshua many cities in Eretz Yisrael did have a wall.

[Nowadays several cities in this country celebrate Shushan Purim. Here in Jerusalem we celebrate Shushan Purim and where I live - in Ramot in the north of Jerusalem - most people celebrate Shushan Purim even though Ramot is slightly separate from the main part of the city.]

(4) Yes we can. The Mishnah (above 17a) states that if a person who only understands a foreign language heard the Megilah in Hebrew he thereby fulfilled the Mitzvah. The Gemara 18a asks how can this be - he does not know what they are talking about? The Gemara answers that he is no different from uneducated Hebrew speakers who fulfill the Mitzvah by hearing the Megilah even though they do not understand everything said in it.

The Gemara adds that in fact even the best-educated Hebrew speakers also do not fully understand the Megilah because nobody knows the real meaning of "the Achashteranim the sons of the Ramachim" (Esther 8:10). This forces us to say that there are 2 components of the Mitzvah of Megilah (a) the mitzvah of reading it (b) the publicizing of the miracle. If someone does not understand what is said in the Megilah he will ask other people and they will explain it to him and how the miracle came about.

(5) This is explained by the Ritva DH Ella Matan who writes that this is derived from the verse (Esther 8:9) " Each people and people according to its tongue". This teaches us that in the tongues of the people one can only fulfill the Mitzvah if it is one's tongue that one understands. In contrast, the end of this verse states " And to the Jews - according to their writing and their tongue". Hebrew is a Jew's tongue whether or not he understands it, so one can fulfill the Mitzvah of Megilah in Hebrew even without understanding the language.

KOL TUV

Dovid Bloom

Here is a different answer to question (5):

This is based on Rashi 18a DH u'Pirsumei. As we explained in our previous answer to (4), the Gemara states that even though Hebrew speakers also do not understand every word - because we do not know what the words "Achashteranim the sons of the Remachim" means - nevertheless Hebrew speakers still are able to fulfil the Mitzvah of reading the Megillah and publicising the miracle. The Gemara concludes that by the same reasoning a foreigner who hears the Megilah in Hebrew also thereby fulfils the mitzvah because the Megilah was read and the miracle is publicised and this is sufficient even if one does not understand the literal translation of every single word.

Rashi explains that even though the non-Hebrew speakers in the Hebrew audience do not know what they are listening to, nevertheless they will ask others in the congregation what the reading is about, and how the miracle happened, and this way the Hebrew speakers will tell the non-speakers about it.

This is all feasible for a Jewish guest in Hebrew speaking circles. Firstly most Jews, even though they might not be fluent in Hebrew, nevertheless at least know a few words and therefore do at least have some vague idea of what is being said by the Reader of the Megilah. (In addition, even though they are in a Hebrew audience, it is likely that they will find someone in the community who also speaks their foreign language. This is similar to a contemporary scenario when, for instance, a French Jew visiting Israel, will probably find other French-speakers to help him out).

In contrast if the non-Hebrew speaker hears the Megilah in a different foreign language, he will probably not understand what is being said at all, because it is likely that he does not know a word of what is being read. (In addition the French visitor in China in all likelihood has no-one in the congregation who can help him out). So he will not even know what to ask about the reading he is hearing. Because he does not know where to start he therefore will never find out what the Megilah was about and there will be no "Pirsumei Nissa" - publicising of the miracle of Purim.

KOL TUV

Dovid Bloom