Short answers, pulled from the story.
Modern archaeological evidence places the start of large-scale global iron production about 1200 BC, marking the end of the Bronze Age. In Anatolia, the Caucasus, or Southeast Europe the Iron Age began around 1300 BC, while Northern Europe was not reached until about the 5th century BC.
The Iron Age is defined locally when the production of smelted iron, especially steel tools and weapons, replaces their bronze equivalents in common use. The characteristic mark is the mass production of tools and weapons made from smelted steel alloys with added carbon, not merely the presence of found iron.
Anthony Snodgrass suggests a shortage of tin and trade disruptions in the Mediterranean about 1300 BC forced metalworkers to seek an alternative to bronze. When tin became available again, iron was already cheaper, stronger, and lighter, and forged iron implements superseded cast bronze tools permanently.
Smelting terrestrial iron requires temperatures above 1250 degrees Celsius, impractical to achieve with technology commonly available until the end of the second millennium BC. Bronze was far easier, since tin melts at 231.9 degrees Celsius and copper at 1,085 degrees Celsius, both within reach of Neolithic kilns that produced temperatures greater than 900 degrees Celsius.
No. The Iron Age began at different times in different regions, and in some areas the concept does not fit at all. Africa lacked a universal Bronze Age and many areas moved directly from stone to iron, while in China writing developed before iron smelting, so the term is used infrequently there.
Christian Jürgensen Thomsen introduced the Iron Age as an archaeological era to Scandinavia during the 1830s. The three-age system of Stone, Bronze, and Iron Ages was first used for the archaeology of Europe during the first half of the 19th century, its name harking back to the mythological Ages of Man described by Hesiod.