1) It is a compilation of apocalyptic and didactic material, ascribed to the antediluvian patriarch Enoch, describing his journeys of heaven and hell (as a sort of a precursor of Dante), as well as visions of the future Judgement Day. It was written between 250 BC (starting with the Astronomical Book) and AD 50 (The Book of Similitudes).
2) The book(s) was written in Judea before the destruction of Jerusalem. The oldest known copies, antedating Christianity, were found in the Dead Sea Scrolls. It was also translated in Greek and used by Hellenistic Jews and Christians, and finally it was translated into Ethiopic where it still forms part of the canon of the Old Testament in the Abyssinian Church.
3) Yes. Especially Jude, but also there is also extensive influence in Revelation, which draws on Enochian motifs (such as binding Satan in an "abyss," the notion of an "abyss" is not found in the OT but comes from 1 Enoch). The synoptic gospels also probably draw their "Son of Man" apocalyptic motifs from the "Book of Similitudes" in 1 Enoch, with some very striking parallels in wording.
4) 1 Enoch 1:9 is explicitly quoted in Jude 14-15. This letter contains about five or six other parallels in wording with 1 Enoch and verbal allusions abound throughout the NT.
5) The author of Jude considered it inspired, referring to the oracles as "prophecy". It was also widely used by early church fathers (cf. 1 Clement, Barnabas, Tertullian, etc.), but it did not gain canonicity as part of the OT for two reasons: (1) It was not already included in the Greek Septuagint which included apocryphal books, and (2) The closed Hebrew canon did not even include the apocryphal books. Whether one was following the narrow canon of Jerome or the wider canon of Augustine, 1 Enoch would have lay outside the bounds of canon. However, it continued to be used and regarded by some as inspired and as Scripture (and by others as a forgery), and was still read, but was not regarded as authoritative (canonical). The canonicity of Jude was doubted by many for some centuries because of its use of 1 Enoch.
6) Yes, they referred to it as "uninspired" and for a while claimed (I think) that perhaps the author(s) of 1 Enoch used Jude, which is completely untenable because the passage of 1 Enoch 1:9 is extant in one of the Aramaic copies of 1 Enoch dating to about 50 BC. They also say perhaps Jude used a genuinely ancient tradition that also coincidentally got used in 1 Enoch, but this is a case of special pleading and untenable considering Jude's many other allusions to 1 Enoch.
I am working on a thread on Jude's use of the pseudepigrapha where I hope to go into more of the specifics.
