The number of Fulfillment Orders that would be created for this order is one per destination, totaling 3. A Fulfillment Order is a record that represents a group of products in an order that are fulfilled together from the same location. A Fulfillment Order has a lookup relationship to the Order Summary object, and it contains information such as the fulfillment location, delivery method, status, etc. The number of Fulfillment Orders created depends on three factors: Fulfillment Location, Delivery Method and Recipient Address. These factors determine how the Order Items are grouped and allocated to Fulfillment Orders based on routing rules and inventory availability. In this case, since the products must be shipped to three different locations, three Fulfillment Orders are created for each destination. Verified Reference: https://help.salesforce.com/s/articleView?id=sf.order_management_fulfillment_order.htm&type=5

The best way for the administrator to satisfy this requirement is to edit the Lightning Record Page and change the Template to Three Regions. A Lightning Record Page is a type of page that displays details and related information about a specific record in Lightning Experience or Salesforce mobile app. A Lightning Record Page can be customized using the Lightning App Builder, which is a tool that allows administrators to drag and drop components onto a page layout. A Template is a predefined layout that determines how components are arranged on a page. A Three Regions template is a type of template that divides the page into three columns or regions. The administrator can edit the Lightning Record Page for the Order Summary object, and change the Template to Three Regions in the Lightning App Builder. Verified Reference: https://help.salesforce.com/s/articleView?id=sf.lightning_app_builder_customize_lex_pages.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.lightning_app_builder_templates.htm&type=5

Two practices that are needed for a custom attribute to map into Order Management assuming the attribute has been created on the necessary objects are:
The types must match within reason. The data type of the custom attribute in Order Management must match or be compatible with the data type of the corresponding attribute in the external system, such as B2C Commerce or B2B Commerce. For example, if the attribute is a string in B2C Commerce, it must also be a string in Order Management.
The names must be an exact match. The name of the custom attribute in Order Management must be exactly the same as the name of the corresponding attribute in the external system, including capitalization and punctuation. For example, if the attribute is named "kitItem" in B2C Commerce, it must also be named "kitItem" in Order Management.
Verified Reference: https://documentation.b2c.commercecloud.salesforce.com/DOC2/topic/com.demandware.dochelp/OrderManagement/Administration/AdminAttrMgrCustomAttributes.html

Two reasons that could cause the issue of not being able to deploy a Change Set from a development org to a test org are:
The development org has not been approved to upload Change Sets from within the test org. To deploy Change Sets between two sandbox orgs, the administrator needs to establish a deployment connection between them. A deployment connection allows one org to send outbound Change Sets and another org to receive inbound Change Sets. The administrator can create a deployment connection request from the development org and approve it from the test org.
The development org and test org are not associated with the same production org. To deploy Change Sets between two sandbox orgs, they must be linked to the same production org. A production org is an org that contains live data and business processes. A sandbox org is a copy of a production org that is used for development, testing, or training purposes. Sandbox orgs inherit the deployment connections of their source production orgs. Reference: Deploy Using Change Sets, Deploy a Change Set

Two reasons an admin should choose an Event over a Trigger when it comes to building out a solution are:
Events are asynchronous. This means that events are processed in the background, without blocking the main execution thread. This can improve the performance and user experience of the solution, as well as avoid governor limits and timeouts.
Events do not participate in a transaction scope. This means that events are independent of the transaction that publishes them, and they do not affect the rollback or commit behavior of the transaction. This can avoid unwanted side effects and errors in the solution, as well as decouple the logic from the data.
Verified Reference: https://developer.salesforce.com/docs/atlas.en-us.platform_events.meta/platform_events/platform_events_intro.htm https://developer.salesforce.com/docs/atlas.en-us.platform_events.meta/platform_events/platform_events_considerations.htm