Setup Salesforce integration with Graph API app registraion process.

Question

Hi,
I am trying to access the Graph Calendar API to create, update and delete the events from users calendar. When I am trying to setup the single tenant app. The app registration process is completed successfully but when I setup on the salesforce side and authentication flow started I got this error
ErrorCode=No_Oauth_Token&
ErrorDescription=invalid_request+AADSTS50194%3A+Application Single+Tenant is not configured as a multi-tenant application.
Usage of the common endpoint is not supported for such applications created after 10/15/2018 Use a tenant-specific endpoint or configure the application to be multi-tenant.
Although we are using the tenant specific urls only. Still this error is returning.
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2. We have one more requirement to create events in Personal accounts and in other tenant user's calendar but the access token is generated for a user which exist in different tenant. Is it possible like if a user from Organization A login in to the system and get the access token and will able to create events in Personal Account calendar and in other user's from Organization B?
   If not possible then how we can achieve this type of scenario with graph api.