Which entity in Magento supports scoped attributes?

The module MyCompany_MyModule will add a new page in the admin interface to display a custom entity in a grid.
You created a controller for this grid \MyCompany\MyModule\Controller\Adminhtml\CustomEntity\Index Which two actions are required to make the new page accessible at the
https://your.store.base.url/admin/my_module/custom_entity URL? (Choose two.)

A merchant asks you to extend customer functionality to allow customer accounts to be associated with two or more billing addresses.
How is this implemented?

In a custom module you are adding a new field to the store configuration. The field will set the value for the configuration path mycompany/mymodule/myoption.
How do you supply the default value for that configuration option?

You are adding a new menu item to the admin backend which will link to a custom backend page.
The declaration of the route:

What do you specify as the menu item action attribute value so it links to /admin/mycompany/mymodule/?