A merchant requires the ability to configure contact information for their brick and mortar stores as a CSV file upload. The module already exists and contains an etc/adminhtml/system.xml file where the new field can be added.
How do you specify the class that will process the uploaded file?

You are developing a module and need to add another column to a table introduced by another module MyCompany_MyModule via db schema.
How do you do that?

You have been asked to display details from the customer's latest order on the customer's account dashboard (customer/account/). You create a new custom template to show the information.
How do you obtain an order repository so you can fetch an order?

You got a notification about error that occurred on a production environment. The merchant gave you the error identifier.
How do you find the error message based on the identifier?

You are building a new module to add extra functionality to the Magento application.You want to works with CustomerData the data stored on the client side. Where initialized sections Cart and Directory-data are on the server side via the classes?