1. Does layout change of a category page from one column to three columns require a customization?
No, the layout can be changed by editing the category options.
2. Which of the following changes requires a code customization: Displaying a banner in the page content area, changing a footer link, changing a product page layout from one column to two columns.
Displaying a banner in the page content area would require a code customization.
Changing a footer link would be handled through the
Changing a product page from 1 column to 2 column is very similar to question 1, but the change occurs on the product page instead of the category page.
3. Does creating a product price attribute require a customization or can this be achieved using native Magento functionality?
This is built-in to Magnto. To do this, create a new attribute.
4. Could you create a “How did you hear about us?” customer attribute to collect customer data during purchase and export it to a CSV file using Magento native functionality, or would that require a code customization?
No, this would require code customization to add an attribute to the Customer.