Short answers, pulled from the story.
A mirror is an object whose surface is smooth enough to reflect light waves without scattering them, forming an image of whatever is in front of it. When light waves strike a flat mirror, they bounce back retaining the same curvature and direction they had on the way in, a property called specular reflection. This allows the reflected waves to be focused through a lens and perceived as a coherent image.
The earliest manufactured mirrors were pieces of polished obsidian, a naturally occurring volcanic glass. Examples found at Catalhoyuk in Anatolia have been dated to around 6000 BCE. Mirrors of polished copper followed in Mesopotamia from around 4000 BCE and in ancient Egypt from around 3000 BCE.
The silvered-glass mirror is credited to German chemist Justus von Liebig in 1835. His wet deposition process deposited a thin layer of metallic silver onto glass through the chemical reduction of silver nitrate, and it was subsequently adapted for mass manufacturing.
Venice became the center of a superior tin-mercury amalgam technique for coating flat glass mirrors by the 16th century, and retained that monopoly for about a century. The mirrors could be as large as 40 inches square and were sold as expensive luxury decorations for European palaces. The monopoly ended when the technique was obtained through industrial espionage and French workshops scaled the process to mass production.
A mirror actually reverses front and back, not left and right. The perception of left-right reversal arises because the brain unconsciously imagines the reflected figure has physically turned to face the viewer, just as a real person would, and that imagined rotation is what introduces the apparent swap of left and right hands.
The mirror test measures whether an animal can recognize its own reflection. Animals confirmed to pass include humans (generally from about 18 months of age), all great apes including bonobos, chimpanzees, orangutans, and gorillas, and bottlenose dolphins.