Q. See question above. I wonder do you have to make a seuda on Purim Katan on Friday or since it is Erev Shabbat, should it not be better in the night? How about the people that dwell in a city were Shushan Purim is celebrated?
A. As mentioned Remoh (O.H. 677: 1) writes that there is no requirement to do a seudah at all on Purim Kattan, only to add a bit to the regular meal. On Friday this should be done before chatzos. (midday).
Mishna Berura (ibid. 4) rules that there is no need to add to the regular meal on Shushan Purim even for the dwellers of a city that celebrates Purim on the 15th.
However, Eliahu Rabbah (ibid. 2) and Hisorerus Teshuva (quoted in Nitey Gavriel {Purim 16: n. 20) maintain that some do celebrate Shushan Purim Kattan.
According to this singular opinion, Horav Shlomo Miller Shlit"a suggested that they may celebrate on Sunday.
Rabbi A. Bartfeld as revised by Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu Shlit’a and Horav Kalman Ochs Shlit’a.