FFCC can be done to anyone by anyone, but should only be done for a passenger on a full fare (using full miles or $$, no upgrades) C or F passenger. It is expected that every agent do it in that situation as well. It is not the "level" of the agent, rather, the level of the ticket, which determines if the FFCC is applicable. There are no other protocals that are accepted by UA to add one to that list (it is NOT designed for moving someone ahead of others, although I have seen it improperly used that way.)