1)
Why does it say "Mi Yafer"?
1.
Rashi: Since Hashem wants, no one can annul His counsel. If so, His word will endure; like He said via His Nevi'im, so will be.
2)
What is the meaning of "Yado Netuyah Mi Yeshivenah"?
1.
Malbim: Who can stand in front of Him?!