Out of the following variables, which has the widest range of visibility within the platform?

A new column is added to the recipient schema via a schema extension. The extension is called recipientExt in namespace abc. This new column is called CustomerDecile and is of type long.
What is the database location of the new column?

During development, the client must only send emails to their company domain.
How should a Campaign developer make sure this is enforced?

A client is using Their own Customer schema instead of the default Recipient schema. What out-of-the-box functionality do they lose if they do so?

Which operator group is required to approve the target group in a campaign workflow?