Prompt: As an e-commerce specialist, write a comprehensive guide on how to start an online store from scratch. Include detailed steps on platform selection, website design and development, product sourcing, inventory management, payment processing, order fulfillment including shipping and returns, customer relationship management (CRM), and performance tracking. Provide insights on best practices for optimizing user experience, building trust and security, leveraging online marketing channels, and nurturing customer loyalty. Include case studies and real-world examples to illustrate key concepts.