Calendar Sync Query

1. If we migrate emails of last 7 days and include Calendar, does it migrate all calendar items? 

2. If we migrate calendar items from MAILBOXA exchange 2016 to MAILBOXB EXO, will that delete existing calendar items? We migrated MAILBOXA to MAILBOXB then we migrated MAILBOXC to MAILBOXB, it deleted old calendar items from MAILBOXB. Is it normal behavior? How it is going to sense that source does not have abc calendar item so delete it in target. 

3. How Quest keep track of emails and calendars. Their own generated ID or Exchange ID?