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?

You are creating a new page layout for your custom module.
What is the primary difference between container and block elements?

How do you persist an entity to the database?

Which two ways does Magento persist category relationships in the database? (Choose two.)

In a code review of a merchant's site you have discovered that there are multiple observers for the checkout_submit_all_after event. After closer inspection, you notice one of these observers is relying on the others being executed before it is called.
What risk does this pose, and how can it be mitigated?