Short answers, pulled from the story.
The phrase means the final destiny of the gods rather than simply their death. The first element is the genitive plural of regin meaning ruling powers or gods and the second element rökkr or rök holds meanings including fate, reason, end of the world, and creation of mankind.
A female seer recites information to Odin starting from stanza 40 until 58 of the poem Völuspá. She describes three roosters crowing to signal the coming conflict before the hound Garmr breaks free from the cave of Gnipahellir.
Thorwald's Cross stands on the grounds of Kirk Andreas on the Isle of Man as a partially surviving runestone dated to 940 or the 11th century. It depicts a bearded human holding a spear downward at a wolf with his right foot inside its mouth.
Hilda Ellis Davidson theorizes events occurring after death of gods may be inspired by volcanic eruptions on Iceland. Records of eruptions bear strong similarities to sequence described especially the eruption at Laki in 1783 and massive volcanic eruptions creating dust veil producing broad climatic changes in years 536 and 550.
English-language media outlets widely reported a prediction that the event would occur on the 22nd of February 2014 though no Viking Calendar existed. The Marvel Cinematic Universe released Thor: Ragnarok in 2017 where demon Surtur destroys Asgard and Assassin's Creed Valhalla released in 2020 depicts Ragnarök revolving around Toba Catastrophe solar flare killing most Isu civilization.