Yes, this is exactly what depot separation is about.
No, it will not affect previous reports. But you should go through all ValiChecks as shown here: "How to validate my account?" (https://cointracking.freshdesk.com/a/solutions/articles/29000035339?lang=en)
Here you can find the cost per unit on the gains page - and a depot separation filter is available besides others as well: https://cointracking.info/gains.php