Q. 4) See prior question 1242.What happens if when reciting the sheva brochos, Shehakol was said instead of Hagefen? Mesameach Chassan Vekala instead of Chassan Im Hakala?

A. Horav Shlomo Miller’s Shlit’a opinion is that being under the chupa is not different from any other situation where we rule that when mistakenly reciting shehakol on wine, after the fact one complies.
Similarly, if one would have to perform in need a chupa at a location where kosher wine is not available, he may use beer or any other liquor that is considered chamar medina and recite shehakol instead.
Regarding Mesameach Chassan Vekala instead of Chassan Im Hakala in the last brocho, Kuntres Paamei Yaakov (5768: n. 2) carries a number of articles with different opinions on the same question. Horav Zalman Nechemia Goldberg Shlit’a maintains, that the fact that our sages instituted these changes in the last two brochos, carries a meaning that makes it essential. He suggests on the sheva brochos after the meal, to ask one of the participants that did not hear that brocho to recite it now properly for all to hear. However, under the chupa, where there is no obligation for the attendants to hear, it should be repeated.
Horav Ephroim Greenblatt zt’l opines that after the fact one is yotze and since the change is minimal it is not considered as altering the established matbea of the brocho. So is the opinion of Horav Yisroel Meir Lau Shlit’a and Horav Gavriel Tzinner Shlit’a (Nitei Gavriel)
Horav Shlomo Miller’s Shlit’a opinion is similar.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a