How to access to a public group / public planner

Hi all,

not sure I can find this answer on the online how-to. I need to create a public group (linked to a public planner) because I want invite somebody out of my organization. I understand that, let me quote:

"Select Public to create a group where anyone within your organization can view its content and become a member."

1)

which is fine to me. I don't love it but it's not a big problem. My question is - how do anyone from my organization access to that public planner? I guess they have to type a sort of URL that would take them there, correct? Which URL? For instance I tried https://tasks.office.com/[domain].comfrom another account (same organization) but it didn't work. 

2)

Let's pretend I don't invite a person of my organization, therefore they don't know that planner exists. I guess Outlook will NOT inform them about this public planner, correct? I just don't want to spam everybody about my planner activities if they are not involved.  

3)

I made a test on a public planner. I invited a person not from my organization. Then I tested on how to remove them (kick them out from the group), so I removed the person from the group, and I removed their tasks on the planner, but still, if they click on https://tasks.office.com/[domain].com they can still access to my planner. Why is that?

Sorry for so many questions!!

Thank you all!

Rob