The Fourth Industrial Revolution (4IR) and Mixed Reality (MR) are revolutionizing industries worldwide by merging advanced digital technologies with physical environments. This paper explores the convergence of 4IR technologies, such as Artificial Intelligence (AI), the Internet of Things (IoT), robotics, and big data analytics, with MR, which includes Augmented Reality (AR) and Virtual Reality (VR). Specifically, this article examines the profound impact of these technologies on two distinct sectors: agricultural economics in developing nations and retail experiences in the United States. In developing nations, the agricultural sector faces numerous challenges, including resource constraints, climate change, and limited access to technology. The integration of 4IR technologies is transforming this sector by enabling precision farming, improving resource management, and optimizing supply chain processes. IoT devices and AI-powered algorithms are enhancing irrigation, fertilization, and pest control, while drones and robotics are automating labor-intensive tasks such as planting and harvesting. MR technologies, particularly AR and VR, are playing a vital role in providing virtual training for farmers, real-time monitoring of machinery, and on-site troubleshooting. These innovations significantly improve agricultural productivity and sustainability, leading to higher yields, more efficient resource use, and better livelihoods for farmers. In contrast, the retail industry in the United States is undergoing a digital transformation fueled by the rise of e-commerce and evolving consumer preferences. MR technologies are at the forefront of this transformation, offering personalized and immersive shopping experiences that enhance customer engagement. AR allows consumers to virtually try on clothing, accessories, and cosmetics, while VR creates immersive brand experiences and virtual stores. These innovations not only enhance the shopping experience but also streamline supply chain management and inventory control through AI and IoT applications. The article explores how these technologies enable retailers to deliver personalized recommendations, optimize inventory levels, and improve logistics operations. Through an in-depth analysis of case studies, this paper illustrates how the convergence of 4IR and MR technologies is driving economic growth and operational efficiency in agriculture and retail. It also highlights the challenges and barriers to technology adoption, such as financial constraints, resistance to change, and regulatory considerations. The article concludes with policy recommendations for governments, businesses, and international organizations to foster the broader implementation of 4IR and MR technologies. These recommendations include investing in digital infrastructure, promoting cross-sector collaborations, and providing incentives for technology adoption. By leveraging these advancements, developing nations can improve agricultural sustainability, and the U.S. retail industry can deliver more engaging, efficient, and personalized experiences, ultimately driving sustainable economic development.