What's the difference between "program" and "agenda" when they are used to

Agenda is usually used in the sense of items to be discussed or matters to be resolved in a meeting. It also has the meaning of goals, such as the goals someone has for a meeting or a process. This is where the locution "hidden agenda" comes from--a set of goals which one or more persons have which they have not revealed. I think it is highly unlikely that a native-speaker of English would use agenda as you have used it in your second example. Arriving in Beijing is a function of the airline which takes you there, and evening free is a description of your activity (or lack of activity) and not something to accomplish.