Merlin supports appointments, meetings, tasks, alerts, birthdays or anniversaries, and Sharing and Synchronization events. Depending on the nature of the event, most are automatically linked via the Syndex™ to the people (Contacts) and data (emails, files, etc.) that they relate to. Tasks in Merlin can have an unlimited number of sub-tasks and can be arranged in time-lines or hierarchically.
Yes. Merlin allows you to create an unlimited number of calendars for any sort of special purpose you have in mind, such as holiday or vacation schedules, calendars for special events, or for specific people (Contacts). Custom calendars can be synchronized across your devices and contacts just like your primary calendar.
No, but you can override that. Merlin is a secure 'closed ecosystem'. Systems such as MS Exchange or Google Calendar are insecure, so linking any information to them defeats that purpose. That said, you can override that and 'push' events out to external systems, or 'pull' data in from them. Pulling data in represents only a small risk to privacy. Pushing data out represents a larger potential risk to privacy. Individual events marked as 'private' will not be shared, even when you push calendars to external systems.