An Apex trigger creates a Contract record every time an Opportunity record is marked as Closed and Won.
This trigger is working great, except (due to a recent acquisition) Opportunity records need to be loaded into the Salesforce instance.
When a test batch of records are loaded, the Apex trigger creates Contract records. A developer is tasked with preventing Contract records from being created when mass Loading the Opportunities, but the daily users still need to have the Contract records created.
What is the most extendable way to update the Apex trigger to accomplish this?

An org has a requirement that an Account must always have one and only one Contact listed as Primary. So selecting one Contact will de-select any others. The client wants a checkbox on the Contact called 'Is Primary' to control this feature. The client also wants to ensure that the last name of every Contact is stored entirely in uppercase characters. What is the optimal way to implement these requirements?

Given the following code:

Assuming there were 10 Contacts and five Accounts created today, what is the expected result?

A developer used custom settings to store some configuration data that changes occasionally. However, tests are now failing in some of the sandboxes that were recently refreshed.
What should be done to eliminate this issue going forward?

An org records customer order information In a custom object, Orcer__c, that has fields for the shipping address. A developer is tasked with adding code to calculate shipping charges on an order, based on a fiat percentage rate associated with the region of the shipping address.
What should the developer use to store the rates by region, so that when the changes are deployed to production no additional steps are needed for the calculation to work?