Short answers, pulled from the story.
The earliest representations of what might be the Set animal come from a tomb dating to the Amratian culture, which existed between 3790 and 3500 BCE. If those early images are ruled out, then the first clear appearance of the Set animal appears on a ceremonial macehead belonging to Scorpion II during the Naqada III phase.
The meaning of his name is unknown, but it is thought to have been originally pronounced sūti with a guttural sound at the end. Egyptian hieroglyphs spell his name as st or swt, and late Egyptian spellings like st reflect changes in how people spoke the word over time until the final consonant disappeared entirely.
Set is usually depicted as an enigmatic creature referred to by Egyptologists as the Set animal, which has a downward curving snout, long ears with squared-off ends, and a thin forked tail with sprouted fur tufts. This beast is not identified with any known animal, although it could resemble a Saluki, aardvark, African wild dog, donkey, hyena, jackal, pig, antelope, giraffe, or fennec fox.
According to Herman te Velde, the demonization of Set took place after Egypt's conquest by several foreign nations in the Third Intermediate and Late Periods. Set had traditionally been the god of foreigners, so he also became associated with foreign oppressors including Kushite and Persian empires while his negative aspects were emphasized during this period.
Set was worshipped at temples of Ombos near Naqada and Ombos near Kom Ombo, at Oxyrhynchus in Middle Egypt, and also in part of the Fayyum area. More specifically, Set was worshipped in the relatively large metropolitan locale of Sepermeru especially during the Ramesside Period where an important temple called the House of Set Lord of Sepermeru stood.
The Temple of Set founded in 1975 venerates Set as figure of isolation and self-deification emphasizing personal enlightenment and exploration of left-hand path. Kemetism is a modern revival of ancient Egyptian religion acknowledging Set as complex deity associated with chaos storms and warfare yet also protector against serpent Apep.