Short answers, pulled from the story.
On the 25th of August 1912, Lieutenant Piero Manzini became the first pilot to be shot down by ground-to-air artillery fire. This event marked the beginning of a new era in warfare where the sky was no longer a safe haven for aircraft.
Gustav Krupp mounted a modified 1-pounder gun on a horse-drawn carriage to shoot down balloons during the Franco-Prussian War of 1870. This early attempt at anti-aircraft warfare laid the groundwork for the sophisticated systems that would emerge in the decades to follow.
On the 30th of September 1915, Private Radoje Ljutovac fired his cannon at enemy aircraft and successfully shot one down during a bombing raid on Kragujevac. This marked the first occasion in military history that a military aircraft was shot down with ground-to-air artillery fire.
By the start of World War I, the 77 mm had become the standard German weapon and came mounted on a large traverse that could be easily transported on a wagon. Krupp 75 mm guns were supplied with an optical sighting system that improved their capabilities.
In 1935, the British decided to adopt the Bofors 40 mm and a twin barrel Vickers 2-pounder on a modified naval mount. The air-cooled Bofors was vastly superior for land use, being much lighter than the water-cooled pom-pom, and UK production of the Bofors 40 mm was licensed.
Man-portable missiles, known as MANPADS, were introduced in the 1960s and have supplanted or replaced even the smallest guns in most advanced armies. These systems allow individuals to launch surface-to-air missiles against aircraft.