What is the significance regarding the order in which Rivkah answered Eliezer's questions?
Rashi: She answered the questions in the order that they were asked. 1
A sign of intelligence (See Pirkei Avos, 5:7)
Why did Rivkah mention the fact that Milkah gave birth to Besuel from Nachor?
Refer to 24:15:2:1.
Tiferes Yehonason: "Yaldah Milkah Gam Hi" (22:20) shows that Milkah gave birth in her old age (like her sister Sarah). It was a miracle, for Tzadikim who would descend from her (Rivkah, Rachel and Leah).
Ha'Emek Davar (23): Eliezer had said "Hagidi", which implies giving all the details.