What was the exact procedure regarding the blessings and the curses?
Rashi (citing Sotah, 33b) and Targum Yonasan (on Pasuk 15): Six tribe 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 began with B'rachah - "Baruch ha'Ish asher Lo Ya'aseh Pesel ... "), and both groups answered 'Amen'. Then they turned towards Har Eival, and repeated the K'lalah - "Arur ha'Ish asher Ya'aseh Pesel ... ", and again both groups answered 'Amen'. And so they went through the list of B'rachos and K'lalos one after the other.
Rashbam: The six tribes that ascended Har Gerizim answered 'Amen' on the B'rachos, and the six that ascended Har Eival answered 'Amen' on the K'lalos.
Targum Yonasan: it was the first six tribes that recited the B'rachos, and the second six, the K'lalos. 1
Targum Yonasan also translates "ve'Anu ha'Levi'im in Pasuk 14 as 'The Levi'im shall announce!' See Or ha'Chayim.
Why, by the blessings, does the Torah write "ve'Eileh Ya'amdu Levarech es ha'Am", whereas in the following Pasuk by the curses, it writes "ve'Eileh Ya'amdu al ha'Kelalah"?
Rashi: Refer to Bamidbar 23:8:1:1.
Seeing as the Kohanim read both the blessings and the curses, why does the Torah only mention the curses