1)
What is the meaning of "v'Yiske'u Sheloshes ha'Rashim"?
1.
Radak: The three divisions (not only the leaders of them 1 ) blew Teki'ah. This is like "v'Hayah l'Arba'ah Rashim" (Bereishis 2:10).
1
Malbim (verse 22) says that later, they all blew. Perhaps he explains "v'Yiske'u" to mean that they prepared to blow. Or, it means that they blew, and the verses proceed to discuss the order in which they blew. Or Sheloshes ha'Rashim refers only to the leaders of the divisions, unlike Radak. (PF)
2)
When did they call out "Cherev la'Shem ul'Gid'on"?
1.
Malbim: It was before they blew Teki'ah 1 ; they were holding the Shofaros in order to blow Teki'ah.
