1)
To whom is this Pasuk speaking?
1.
Rashi: It is speaking to the Kohen, since we already know that a B'chor is one of the Matnos Kehunah - irrespective of whether it is a Tam or a Ba'al-Mum. 1
1
Rashi: See Bamidbar 18:18.
2)
What are the implications of "Shanah be'Shanah"?
1.
Rashi #1: It implies that one may not hold back a B'chor from the Kohen until the year after it is born. 1
2.
Rashi #2: It implies that one is permitted to eat a B'chor from one year to the next. Assuming it is offered on the last day of its year, it may be eaten on the first day of the following year - which teaches us that a B'chor may be eaten for two days and the night in between
