Short answers, pulled from the story.
The Greek alphabet was derived from the earlier Phoenician alphabet, one of the consonant-only scripts used for West Semitic languages. The Greeks adopted all 22 Phoenician letters and reassigned five of them to represent vowel sounds, creating the first alphabet to systematically write both vowels and consonants. This adaptation is conventionally dated to around 800 BC.
The standard Greek alphabet has 24 letters, ordered from alpha to omega. This 24-letter Ionic-based form, sometimes called the Eucleidean alphabet after the archon Eucleides who proposed its adoption in Athens around 403 BC, became the universal standard across the Greek-speaking world by the end of the 4th century BC.
The Greek alphabet is the ancestor of the Latin, Cyrillic, Gothic, Coptic, and Glagolitic scripts, among others. The Latin alphabet reached Italy via Greek colonists in the late 8th century BC and passed through the Etruscans. Cyrillic was devised in the First Bulgarian Empire based on the Greek uncial majuscule.
Phi Beta Kappa, founded at the College of William and Mary in 1776, used Greek letters as an acronym for its motto, Philosophia Biou Kybernetes, meaning "Love of wisdom, the guide of life." Early fraternal organizations kept these Greek-letter mottos secret and revealed them only to members, which is why the letter names became the public identity of these groups.
In May 2021, the World Health Organization announced that variants of SARS-CoV-2 would be named using letters of the Greek alphabet. The decision was made to avoid attaching stigma to any country or region and to simplify communications for non-scientific audiences.
The system of accent marks for ancient Greek was devised by the scholar Aristophanes of Byzantium, who worked at the Musaeum in Alexandria around the 3rd century BC. He also introduced a series of signs for textual criticism and was the first to divide poems into lines rather than writing them as continuous prose.