1)
What is "ha'Mahpeches"?
1.
Rashi, Targum Yonasan: It is a jail cell. It is a noun.
2.
Radak citing his father: It is a Kli of two sticks, and they make a neck opening in between, and they insert in it the prisoner's neck (a stockade).
2)
Where is "Sha'ar Binyamin ha'Elyon"?
1.
Radak: It is in Binyamin's portion, for the Beis ha'Mikdash was partially in Yehudah's portion, and partially in Binyamin's.