Option B is the correct template to display the details message only when areDetailsVisible becomes true. This is because Option B uses the if:true directive on a nested <template> tag that encloses the conditional content. The if:true directive binds data to the template and removes and inserts DOM elements based on whether the data is a truthy or falsy value1. Option A, C, and D are incorrect because they do not use the if:true directive on a nested <template> tag, and therefore will not render the content conditionally. Reference: 1: Render HTML Conditionally - Trailhead2

After updating a Page Label record, you must rebuild and activate the Configuration Cache in order to see the changes reflected in the storefront. This is because the Configuration Cache contains all of the static data that is used to render the storefront, including Page Labels.
Reference:
Salesforce B2B Commerce Administrator Trailhead module: https://trailhead.salesforce.com/content/learn/modules/b2b-commerce-basics

To set up a storefront from scratch, the developer can use the sfdx commerce:store:quickstart:setup command, which performs all the necessary steps to create a storefront, push store sources, create buyer users, import products, and create and search index. The command requires a definition file that specifies the store name, template name, and other parameters. For example, a store-scratch-def.json file could look like this:
{ "storeName": "test-store", "templateName": "b2c-lite-storefront", "orgName": "Test Org", "edition": "Developer", "features": ["Communities", "B2BCommerce"], "settings": { "communitiesSettings": { "enableNetworksEnabled": true } } } The developer can then run the command as follows:
sfdx commerce:store:quickstart:setup -definitionfile store-scratch-def.json This will create a test-store storefront using the b2c-lite-storefront template in a scratch org named Test Org with Developer edition and B2B Commerce features enabled. The other options are not correct because:
sfdx commerce:store:quickstart:create -templatename 'b2c-lite-storefront' is an invalid command. There is no quickstart:create command in sfdx commerce:store.
sfdx commerce:store:create -store-name test-store is a valid command, but it only creates a storefront with a default template. It does not push store sources, create buyer users, import products, or create and search index.
sfdx commerce:store:open -store-name test-store is a valid command, but it only opens an existing storefront in a web browser. It does not set up a storefront from scratch