1. Said Hamotzi instead of Mezonos on the Mezonos bread or snack:

Said Hamotzi instead of Mezonos on Pas Haba Bekisnin:[1] If one accidentally recited the blessing of Hamotzi on a baked Mezonos food which is defined as Pas Haba Bekisnin, then one fulfills his obligation and the blessing of Mezonos is not to be recited.[2] This applies even if one did not set a meal over the Pas Haba Bekisnin food. Upon finishing eating, one recites the regular after blessing of Al Hamichyeh and not Birchas Hamazon, unless he ate enough to require Birchas Hamazon.

Said Hamotzi instead of Mezonos on a Mezonos food that is not Pas Haba Bekisnin:[3] If one accidentally recited the blessing of Hamotzi on a Mezonos food which can never become Hamotzi [i.e. cooked pasta, deep fried Sufganiyot donuts, cholent with grains, oatmeal porridge, etc], then one does not fulfill his obligation and must repeat the correct blessing of Mezonos on the food.[4] [Hence one is to immediately say Baruch Sheim Kevod Malchuso Leolam Vaed and then recite the correct blessing on the food. If one corrected himself within Kdei Dibbur then he is Yotzei as explained in Chapter 7 Halacha 19.]

[1] Mamar Murdechaiy 168:18; Chayeh Adam 58:1-2; Derech Hachaim Dinei Taus Alef; Kitzur Shulchan Aruch 56:1; Kaf Hachaim 158:43; Birchas Habayis 19:22; Even Haozer 168:5; Ketzos Hashulchan 48 footnote 1; Ritva Brachos 2:18; Igros Moshe Y.D. 3:120 -2 unlike Igros Moshe O.C. 2:54

Other Opinions: Some Poskim rule that the blessing of Hamotzi never covers Mezonos, even by Pas Haba Bekisnin, and hence the blessing of Mezonos is still required to be recited. The proof is from the fact that regarding those breads which are disputed whether they are Hamotzi or Mezonos it is ruled that Mezonos is to be recited. This implies that if one were to recite Hamotzi then he would not fulfill his obligation according to the opinion which requires Mezonos to be said. [Elya Raba 168:20; Igros Moshe O.C. 2:54 unlike Igros Moshe Y.D. 3:120 -2]

[2] The reason: As these foods contain the same form as does bread and thus it does not appear that one is lying when saying the blessing. [Chayeh Adam ibid]

[3] Mamar Murdechaiy 168:18; Chayeh Adam 58:1-2 and Nishmas Adam 1; Derech Hachaim Dinei Taus Alef; Kitzur Shulchan Aruch 56:1; Kerem Shlomo 168:5; Ketzos Hashulchan 48 footnote 1; Kaf Hachaim 158:43

[4] The reason: As it appears like a clear lie to say “Hamotzi” over this food when in truth it has no resemblance of bread. [Chayeh Adam ibid]