Does the customer have to use a countertop on top of the base cabinets?

We can make a full top from the same material as the cabinet box. We can do this but we do not advertise it.

How long does the countertop need to be in order to need a countertop bracket?

This really depends on the scenario but it is usually around 48" when the countertop needs extra support.

How is the countertop backsplash attached?

It is attached to the wall with construction glue. (not provided)

How much is the countertop per inch?

The black impact coating is $7.04 per inch. The maple butcher block is $9.01 per inch The laminate is $5.40 per inch