79:7 When Rosh Chodesh falls on Shabbos, we read the section starting with Isaiah 66:1 for the haftarah. If the reader erred and read the regular haftarah for that week’s parsha, if he has not yet recited the concluding brachos, he can say also the Shabbos Rosh Chodesh haftarah and then the brachos. If he only realized his mistake after the brachos, he can read the Shabbos Rosh Chodesh section without any brachos. When Rosh Chodesh falls on Sunday, we read the section starting from I Samuel 20:18, “Tomorrow is the new moon,” as the haftarah. If one mistakenly read the regular weekly haftarah, the procedure is the same as when Rosh Chodesh falls on Shabbos. If Rosh Chodesh falls on both Shabbos and Sunday, we read the haftarah from Isaiah 66.
79:8 On the Shabbos of chol hamoed Pesach, we don’t mention yom tov in the brachos after the haftarah, neither in the middle of the bracha, nor at the end. Rather, the bracha simply concludes that G-d sanctifies Shabbos. On chol hamoed Succos, however, we do mention the holiday, the same as we do when yom tov falls on Shabbos. This is because every day of Succos has its own unique sacrifice (which makes each day of Succos like its own yom tov – Mishnah Brurah 490:16); this is also the reason full Hallel is recited every day of Succos.