Short answers, pulled from the story.
The United Nations Department of Economic and Social Affairs traces its modern form to a 1997 merger. Three distinct departments combined forces that year including the Departments for Policy Coordination and Sustainable Development, the Departments for Economic and Social Information and Policy Analysis, and the Department for Development Support and Management Services.
The adoption date of the 2030 Agenda for Sustainable Development was the 25th of September 2015. This framework includes the 17 Sustainable Development Goals adopted by the UN General Assembly and serves as a foundation for work within the United Nations Department of Economic and Social Affairs.
Since 2007, positions within the United Nations Department of Economic and Social Affairs have been held by representatives from the People's Republic of China. This change marked a new era for the department's direction and reflects broader changes in how developing nations engage with UN bodies.
The United Nations Department of Economic and Social Affairs supports the Second and Third Committees of the General Assembly. These committees handle critical issues related to human rights and decolonization while the department also provides direct services to the United Nations Economic and Social Council.
The DDSMS component began life in 1978 as the Department of Technical Cooperation for Development. It kept that title until 1993 when it changed names again before merging into what is now called UNDESA.