To override the parent theme styles, the developer needs to change the web/css/source/_extend.less file in the child theme. This file is used to import and extend the parent theme styles without modifying the original files. The developer can use the @import directive to import the parent theme styles and then use the .lib-css() mixin to override the CSS properties. For example:

@import ‘source/_extend.less’; // Import parent theme styles .lib-css(color, red); // Override color property

The web/css/source/_extends.less and web/css/source/_theme.less files are not valid and will not work, as they do not follow the theme structure or the naming convention. References: [Theme inheritance], [Extend parent theme styles]

The styles-l.less and styles-m.less files are two main LESS files that are used to generate CSS files for different devices and screen sizes. The styles-l.less file is used to generate styles-l.css, which contains desktop-specific styles that are applied only when the screen width is greater than 768px. The styles-m.less file is used to generate styles-m.css, which contains basic and mobile-specific styles that are applied for all devices and screen sizes. The other options are not correct and do not reflect the purpose of these files. References: [Stylesheets], [Responsive web design]

To initialize a JavaScript component using a data attribute, the developer should use the data-mage-init attribute. This attribute allows the developer to specify the name and configuration of the component in a JSON format. For example:

This will initialize the nav component from the Vendor_Module/js/nav file with the given options. The data-bind and data-init attributes are not valid and will not work, as they are not supported by Magento. References: [JavaScript initialization], [data-mage-init]