how many favors are allowed daily and is there a certain time when you will have favors?
In general, you get a favor for every 4 completed cases. (completed favor+3more cases) So if you are unsubscribed, and you have to drop a case or get a false accusation, you won't get a favor that day.
But they are not limited. So if you are in agency and pick cases from others you could (theoreticaly) do as many as you want.