SSO for multiple clients' AD

Hi - I am in discussions with clients (companies) who use MS Office 365, and who would normally expect to be able to use Single Sign-On with their Office365 accounts.

I have little experience with this - so I need some good pointers here.

  1. If I have multiple clients, each with a different domain/(tenant?) at Office365 - can I connect all of them using Auth0? Which solution should I use? Does it require setup in their own Office365 administration panels?

  2. My clients typically share their work over my SaaS solution with their own clients. Their own clients typically have another Office365 domain of their own. My client says they would like to share their work directly with their clients - so that their clients can sign on with SSO for their own Office365 domain. Is this possible? Even without any setup at my client’s client’s (2 degrees separated from me) Office365 admin panel?

  3. My client shares a MS Sharepoint group with their own clients. That sharepoint group then has information about who is in that group. Is it possible to access that group info somehow - if my client is signed on with Office365/SSO?

Many questions here - and I have no experience with these enterprise/sso solutions. Hoping Auth0 could solve these issues?