How to use manager agent

[skim0011]

crew = Crew(
agents=[distributor_agent, q_agent, a_agent],
tasks=[overall_task, task_distributor, task_q, task_a],

manager_agent=manager_agent, 

process=Process.hierarchical,
verbose=True,
memory=False, 

)

My intention was like below to separate agent and task:
distributor_agent => task_distributor
q_agent => task_q
a_agent => task_a

I tried this code, manager agent ran all the tasks.

I can still get a right answer if I move each task to each agent's prompt. But I believe separating task & agent has a benefit(and I guess that's why how crew ai designed that way?)

Q1 - can I still have multiple tasks when I use manager agent?
Q2 - Is there any complicated use cases of manager agent?
Even the crewai's researcher & writer & manager sample code doesn't run properly when I ran it, the task was done by researcher & manager only.