1.Organization Sharing is configured to share calendar information with Microsoft 365 and Office 365 organization or with an Exchange on-premises organization on organization level.
Individual Sharing is configured to let users share calendars with individual business associates, friends, or family members on per-user level via assigning a sharing policy to the user's mailbox.
2.Sorry would you please clarify on External organizations in Sharing Terms?
3.Please see the following screenshots:
free/busy with show meeting titles and locations:
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