ebm

Newbie mom here. Before this I just df my baby so now I'm going back to work. Regarding ebm, 1. Can I mix frozen with chilled/fresh ebm from different date but same temperature 2. Can I mix frozen ebm from different date? 3. If both are not doeable, how do i manage ebm? Baby drinks 3oz per session, but every time i pump i will get 4 or 5 oz. What do i do with the rest of the milk if i pack 3 oz only?