1)
What is "Kohen ha'Rosh"?
1.
Radak: It is the Kohen Gadol, who is the head of the other Kohanim.
2)
What is "Kohen Mishneh"?
1.
Radak citing Targum Yonasan: It is the Segan, who is second to the Kohen Gadol.
3)
What are "Shomerei ha'Saf"?
1.
Refer to 12:10:4:1-2 and the note there.