Why does the Torah write here " v'Hiktiru Oso", in Pasuk 11 "v'Hiktiro" and in Pasuk 16 "v'Hiktiram"?
Ramban: To expound from "v'Hiktiru Oso" - that one may not burn on the Mizbe'ach a Korban that is Pasul; from "v'Hiktiro" - that one may not burn on the Mizbe'ach the Emurim of two animals together. And from "v'Hiktiram" - that one must burn all the Emurim of one Korban simultaneously.
What does the Torah mean when by "al ha'Olah"?
Rashi: It means besides the Olah (which has already been brought), implying that the Olas Tamid is always the first Korban to be brought each morning. 1
See also Sifsei Chachamim.
Why does the Torah write here "v'Hiktiru" (plural), and in Pasuk 11 "v'Hiktiro" (singular)?
Moshav Zekenim (1): Tzon are small, so one Kohen can burn (all the Eimurim). Cattle are big, so more than one Kohen is needed.