# After the fact if one recited Birkat Hamazon on shivat haminim one doesn't fulfill one's obligation.<ref>Even though the Rashbam
Pesachim 103b writes that if mein shalosh is effective on a food then certainly birkat hamazon is effective. This is also found in the Baal Hameor Pesachim 24b but Ramban rejects it. Additionally, Tosfot Pesachim 103a rejects this types of kal vchomer. Tosfot Rabbenu Yehuda Brachot 41b s.v. maskana, Rashba 42a s.v. yayin, and Rosh Pesachim 10:10 agree with the Tosfot against the Rashbam. Shulchan Aruch OC 208:17 follows the Tosfot unlike the Rashbam. The Mishna Brurah 208:75 accept this ruling of Shulchan Aruch. Aruch Hashulchan 208:27 explains that the reason it doesn't work is because only the original bracha that chazal instituted for that food works and nothing else. The only exceptions are when the bracha would have been relevant even according to chazal but practically didn't establish it for some reason (such as for wine and dates).</ref>
# After the fact if one recited Al Hamichya for Birkat Hamazon one fulfills one's obligation.<ref>Raah (Brachot 44a) explains that since Al Hamichya is Biblical and the pasuk which indicates the obligation for Birkat Hamazon includes the obligation for Al Hamichya if one says Al Hamichya in place of Birkat Hamazon after the fact one fulfills one's obligation. This is also the opinion of the Bet Yosef 168:6 who rules that for all forms of pat haba bkisnin one should recite Al Hamichya even though potentially it could be bread.
Gןinat Veradim 1:24, Birkei Yosef 167:10, and Birkat Hashem 2:3:18 agree. The Ginat Veradim explains that this idea is based on the Kesef Mishna Brachot 2:1 who quotes the Rambam and Ramban that Birkat Hamazon is deoritta but the number of brachot are derabbanan.</ref>
# After the fact if one recited Al Hamichya for Boreh Nefashot one doesn't fulfill one's obligation.<ref>Shulchan Aruch OC 208:13</ref>