Short answers, pulled from the story.
The word Stavka comes from an old Russian term meaning tent. In the late 19th century, this name described the administrative staff of the Imperial Russian armed forces and referred to the General Headquarters itself.
The first Stavka was established in Baranovichi during World War I. By August 1915, German advances forced a relocation to Mogilev where it remained until 1917.
Joseph Stalin signed a top-secret decree establishing the Stavka of the Soviet Armed Forces on the 23rd of June 1941. This document named Marshal Semyon Timoshenko as president of the new body.
President Zelenskyy issued Decree No. 72/2022 on the 24th of February 2022 establishing the modern Stavka. This action responded directly to the Russian invasion of Ukraine occurring on that exact date.
Mogilev became the physical home for the Stavka between 1915 and 1917 while headquarters divided into several distinct departments to manage operations. A Department of General-Quartermaster handled all operational planning, another managed troop organization and supplies, military transportation formed its own division, a Naval department oversaw sea-based operations, and a Diplomatic chancery liaised with the Ministry of Foreign Affairs.