Embarking on this PhD journey has been a remarkable experience, made possible through the invaluable support and encouragement of numerous individuals. First and foremost, my deepest gratitude goes to my supervisor, Prof. Luu Anh Tuan, whose continual guidance, motivation, and insightful feedback have been instrumental in shaping my research and my development as a scholar. I am also profoundly thankful to Prof. Xavier Bresson, who supervised my work during the initial two years of my PhD program. Under his guidance, I gained foundational knowledge in the field and learned the rigors of executing research projects. I am exceedingly fortunate to have had the opportunity to work under the guidance of both Prof. Anh Tuan and Prof. Xavier. I would also like to thank Prof. Liu Yang and Prof. Hung Dinh Nguyen for advising me as part of my thesis advisory commmittee. My parents, Mr. Shiva Shankar Dwibedi and Mrs. Lila Dwibedi, have been a constant source of inspiration, teaching me to be ambitious and resilient from an early age. Their unwavering love and support has served as my bedrock, empowering me to persevere through challenges. I extend my heartfelt thanks to my brother, sisters and brother-in-laws for their love and moral support throughout this journey. I had the privilege to intern at Sony Group Corporation in Tokyo, Japan, and Snap Inc. in Seattle, USA, which significantly enhanced my PhD experience. I would like to express my gratitude to Ishii Masato, Takuya Narihira, and Teruaki Hayashi at Sony for broadening my understanding of real-world applications. Special thanks go to my fellow interns at Sony-Siddartha, Aakash, Jai, Noel, Sri, and Christian-with whom I created lasting memories. Similarly, I am grateful for the mentorship provided by Tong Zhao, Neil Shah, and Yozen Liu at Snap Inc., as well as the journey shared with fellow colleagues-Shubham, Yushun, Clark, Zhichun, William, Ankit, Asket, and Anupam. My time in Seattle was further enriched by the friendship of Utsav, Reecha, Bidur, Suman, Sandeep, and Kriti, who made me feel at home. ix x I owe a debt of gratitude to Chaitanya Joshi, whose stimulating discussions during my early days at NTU sparked many research ideas. My colleagues Xiaoyu, Peng and Victor, who were also part of the same lab during my initial period at NTU, deserve special mention for numerous chats and their support.