You have created a new block and will be adding this block on every page. The block contains user-specific information and cannot be cached. The block is added to the default.xml with:

What does this accomplish?

You are tasked with ensuring customers who log into the site are authorized. By default, this consists of ensuring the customers email and password match the values in the database. On this project, you need to verify additional data in this process.
Keeping in mind upgradeability, how is this done?

You are reviewing a Magento module and see a directory named Service.
What can you determine from this directory's name?

You have created a custom module which must perform an action immediately after an order is placed, but only on the store front of the merchant site. You have selected the checkout_submit_all_after as the target event which the module will observe.
In which file will the event observer be declared?

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?