1)
What are the two "Alehah"s coming to preclude?
1.
Menachos, 59a: "Venasata alehah Shemen" precludes the Lechem ha'Panim from containing Shemen, and "Vesamta alehah Shemen", the Minchas Nesachim (that accompanies a Korban) from containing Levonah.
2)
Why does the Torah add (the otherwise superfluous) words "Minchah Hi"?
1.
Menachos, 59a: "Minchah" includes the Minchah of the eighth day of the Milu'im in the Din of Levonah, whereas "Hi" precludes the Sh'tei ha'Lechem from both Shemen and Levonah.