Who wrote the last Bracha of Shmone Esre "Hamivarech Et Amo Yisrael Bashalom" I have heard that there are three halachot for that Bracha, what would they be?

The Talmud Megilah 17b notes that the Beth Din of Ezra the scribe in conjunction with some prophets, have established and composed the 18 blessings of the Shmone Esre Amidah. In the last three of these (which contain the "Sim Shalom") are thanks giving to Hashem and no private requests should be asked then. (see Rambam; Tfilah 1, 4)