A. Scheduled events are executed by using a <CFHTTP> agent.
A2:
B, C, and D. There is no ADD action; UPDATE will add if the task does not exist. DELETE and RUN are valid.
A3:
B and C. weekly is valid; hourly is not (to accomplish that, you'd need to specify 3600 as the number of seconds). 90 seconds is valid; 15 is not (60 seconds is the shortest interval allowed).