In Bootstrap Sass, customization is achieved by using mixins, which are included using the @include directive. Mixins allow the inclusion of predefined styles and functionality in components.

The 'active' class is employed in Bootstrap to customize the appearance of the active state for navigation links. When applied, it visually indicates which page or section is currently active in the navigation menu.

To include a footer in a Bootstrap card, you use the 'card-footer' class followed by the content you want to add. The 'footer' option is the correct choice to achieve this.

Bootstrap offers performance optimization techniques like minifying and concatenating CSS and JavaScript files. These practices significantly reduce the load time of e-commerce websites by minimizing file sizes and improving resource delivery.

To customize the behavior of a Bootstrap dropdown using JavaScript, you can use event listeners to capture the 'show' and 'hide' events. This allows you to add your custom logic to modify the dropdown's behavior based on these events. For example, you can dynamically change the dropdown content or prevent it from closing under certain conditions.

The 'viewport' meta tag is essential in Bootstrap for achieving responsiveness on mobile devices. It sets the viewport width and initial scale for proper rendering.

In Bootstrap, the primary method to customize a theme's color scheme is to override default styles with custom CSS. This allows you to tailor the colors according to your design preferences without directly modifying the Bootstrap files.

Nested grids in Bootstrap enable the creation of multiple levels of grid structures within a page layout. This is useful when you need to organize content into more complex arrangements. To implement nested grids, you can simply include additional grid structures (rows and columns) within the columns of the parent grid. This way, you can achieve a more intricate and flexible layout design.

Bootstrap's grid system is fundamental to responsive web design, allowing developers to create flexible layouts that adapt to different screen sizes. This ensures a consistent and visually appealing presentation across devices.

The $theme-colors map in Bootstrap is significant as it specifies the primary and secondary colors for theming. This map allows developers to define a color palette that aligns with the visual identity of the website. By customizing these colors, developers can ensure a cohesive and branded appearance throughout the application.

The primary purpose of the Bootstrap Tooltip component is to display additional information when a user hovers over an element. It provides a simple and effective way to enhance the user experience by offering context-specific details without cluttering the interface.

Bootstrap provides a flexible grid system, and the 'row' class is used to organize Bootstrap cards into a responsive grid layout. The 'container' class is used for the overall container, but for arranging cards, 'row' is the correct choice.