What was the procedure regarding the B'rachos and the K'lalos?
Rashi: Six tribes ascended Har Gerizim and six, Har Eival, whereas the Kohanim and the Levi'im stood with the Aron in the middle. The Levi'im first turned towards Har Gerizim and proclaimed 1 - "Baruch ha'Ish asher Lo Ya'aseh Pesel ... "), 2 and both groups answered 'Amen'. 3 Then they turned towards Har Eival, and said the curse - "Arur ha'Ish asher Ya'aseh Pesel ... ", and again both groups answered 'Amen'. And so they went through the B'rachos and K'lalos one after the other.
Rashbam: The six tribes that ascended Har Gerizim answered 'Amen' to the B'rachos, and the six that ascended Har Eival answered 'Amen' to the K'lalos.
Targum Yonasan: The first six tribes turned their faces towards Gar Gerizim and recited the B'rachos, and the second six, the K'lalos. 4
Sotah, 37a: Refer to answer #1. They actually stood (not on the mountain, but) beside it 5 and turned their faces towards Har Gerizim for the B'rachos, and towards Har Eival for the K'lalos.
Sotah, 37b: Each of the twelve statements was recited bi'Chelal - first in the form of a blessing - 'Baruch asher Yakim ... ; and then in the form of a curse 'Arur asher Lo Yakim ... ', Arur asher Ya'aseh Pesel ... ' and then bi'Ferat - 'Baruch asher Lo Ya'aseh Pesel ... ... Arur asher Ya'aseh Pesel ... ', and each of these four was given 'Lilmod u'Lelamed, Lishmor Vela'asos' 6 , and the same applied to each of the twelve statements. And Hashem employed the same pattern at Har Sinai and in the Mishkan - 'bi'Chelal u'bi'Ferat, be Baruch u've'Arur', 'Lilmod u'Lelamed, Lishmor ve'La'asos' with regard to all of the Taryag Mitzvos. 7
According to Targum Yonasan in Pasuk 26, all the tribes proclaimed the B'rachos and the K'lalos - but that clashes with what the Torah writes in Pasuk 12. See Na'ar Yonasan there. Moreover, he maintains that they only said the B'rachos pertaining to the first and the last K'lalos - See Oznayim la'Torah. He also says there that all twelve B'rachos and K'lalos were said at Sinai, repeated in the Mishkan and again in Arvos Mo'av, each with a B'ris, making a total of thirty-six B'risos.
See Oznayim la'Torah, as to why the Torah writes only "Arur" and not 'Baruch'.
See Torah Temimah, citing the Yerushalmi Sotah, 7:4
See answer #5 and Na'ar Yonasan.
This is the opinion of Rebbi, who holds that "Al" has connotations of 'beside' (Sotah, Ibid).
Constituting sixteen B'risos - See Torah Temimah, citing Sotah, Ibid and note 23.
Constituting forty-eight B'risos all in all - See Torah Temimah, citing Sotah, Ibid. See also note 1 on answer #1.
Why, by the B'rachos, does the Torah write "ve'Eileh Ya'amdu Levarech es ha'Am", whereas in the following Pasuk by the K'lalos, it writes "ve'Eileh Ya'amdu al ha'Kelalah"?
Refer to Bamidbar 23:8:1:1.
Refer to 27:13:1:1.
Seeing as they recited both B'rachos and K'lalos, why does the Torah only mention the K'lalos?
Seforno: Because the main objective of the Parshah is the K'lalos, to curse those who transgress, inasmuch as they alone will bear their sins and others will not be held responsible for them. 1
Gur Aryeh: Becase the K'lalos were primary, in order that Yisrael should accept the Torah with a curse and Shevu'ah, like Rashi says in Pask 26.
Chidushei ha'Rim: Only the K'lalos are written in order to limit them; the B'rachos are not written because they are unlimited.
Shulchan Shlomoh (in Pasuk 15): It is inappropriate to write a B'rachah for not doing evil. 2 only, since they needed to say the K'lalos, they said also B'rachos. Also, all the B'rachos were said on account of the last one, "Baruch asher Yakim es Divrei ha'Torah ha'Zos" which represents action.
Otherwise, others are liable due to 'Arvus' - accountability for the sins of a fellow-Jew.
Makos 23b: One who was passive and did not transgress is rewarded like one who did a Mitzvah (if he resisted an opportunity to sin -Sha'arei Teshuvah 1:49)! Perhaps we distinguish between reward and B'rachah (PF).
How could Levi, at one and the same time, ascend Har Gerizim and stand in the middle to read out the B'rachos and K'lalos - as the Torah relates in the following Pasuk?
Sotah, 37a #1 (according to R. Eliezer): The elders of the Kohanim and the Levi'im stood in the middle, and the rest of the tribe ascended the mountain.
Sotah, 37a #2 (according to R. Yashiyah): All those who were eligible to perform the Avodah - between the ages of thirty and fifty - stood in the middle, and the rest ascended Har Gerizim.
Ibn Ezra and Metzudos David (in Yehoshua, 8:33): The Kohanim, who were B'nei Levi, 1 stood with the Aron in the middle and read out the B'rachos and the K'lalos, and the Levi'im ascended Har Gerizim.
Following the wording of the Pasuk there - and the current Pasuk is one of the twenty-four places where the Torah refers to Kohanim as 'Levi'im' - See Yevamos, 86b. The Gemara in Sotah, 32a however, states that the Kohanim surrounded the Aron, and the Leviiim surrounded the Kohanim. See Tosfos37a DH 'Iy Efshar'.
Why were Efrayim and Menasheh counted as one tribe?
Oznayim la'Torah #1: Because, when it came to B'rachos, they are always counted as one, as we find both by the B'rachos of Ya'akov 1 and by those of Moshe. 2
Oznayim la'Torah #2: In order to include the tribe of Levi - since there must always be twelve tribes, and not thirteen. 3
QUESTIONS ON RASHI
Rashi writes - in Toldos Bereishis, 27:29 - that Yitzchak mentioned the curse first, because Tzadikim first suffer, and enjoy tranquility at the end. But Bereishis Rabah (66:4) states that Yitzchak loved Yisrael, therefore he concluded with a B'rachah, and conversely, Bil'am concluded with a K'lalah. Also in Re'ei, 11:26-28, the B'rachah precedes the curse, and the B'rachos on Har Gerizim preceded the K'lalos on Har Eival - Sotah 37a?
Refer to Bereishis 27:29:5:3-5 & 27:29:152:1-5 and notes.