Short answers, pulled from the story.
The Z3 was the world's first working programmable, fully automatic digital computer, designed by Konrad Zuse and completed in Berlin in 1941. It was built with around 2,600 relays, used a 22-bit word length, and operated at a clock frequency of about 5-10 hertz. Programs were stored on punched film rather than requiring hardware rewiring.
Konrad Zuse designed the Z3. He had previously built the Z1, a wholly mechanical machine, and the Z2, before completing the Z3 in 1941 under a highly secret German government project. His work led to him being frequently suggested as the inventor of the computer.
The original Z3 was destroyed on the 21st of December 1943 during an Allied bombardment of Berlin. The machine had been renamed from V3 (Versuchsmodell 3) to Z3 to avoid confusion with Germany's V-weapons program.
The Z3 was demonstrated to be Turing-complete in principle in 1998 by computer scientist Raúl Rojas. Because the Z3 lacked conditional branching, achieving Turing-completeness requires speculatively computing all possible outcomes of every branch simultaneously. Rojas noted that from a practical standpoint, the Z3 was not equivalent to modern computers in the way it was actually programmed.
A fully functioning replica built in 1961 by Zuse's company, Zuse KG, is on permanent display at the Deutsches Museum in Munich. A second reconstruction directed by Raúl Rojas and Horst Zuse, completed in 2003, is housed at the Konrad Zuse Museum in Hünfeld, Germany.
Zuse and his colleague Helmut Schreyer proposed an electronic computer using vacuum tubes, but experts at the Telecommunication Institute at Technische Universität Berlin considered the idea practically infeasible given the limitations of tube technology at the time. When Zuse and Schreyer pitched an electronic computer project to the Oberkommando der Wehrmacht in 1940 and estimated a two-to-three year timeline, the proposal was rejected, leading Zuse to build the Z3 using relays instead.