You are adding an entry to the backend menu. To do so you open a core etc/adminhtml/menu.xml file as a reference. In the file you see the node:

What is the result of specifying resource="Magento_Catalog::catalog"?

You want to remove a column introduced by a third-party extension via declarative schema.
How do you do that?

You are setting up a brand new Magento installation for a merchant who is migrating from Magento 1 to Magento 2.
Keeping in mind upgradability and the need to customize, which one do you choose?

In layout files you can change al element's order on a page. This can be done using one of the following:
<move> instruction
before and after element attributes?
How are two methods different?

Your module, MyCompany_MyModule, is using the frontName mymodule. You need to locate the class
responsible for the frontend path /mymodule/custom.
What file contains the controller class for the frontend path /mymodule/custom?