I knew I'd start something there! In New Testament times, what Christians call the Old Testament existed certainly in two languages, Greek and Hebrew, and possibly a third, Aramaic. The known Aramaic texts (known as Targums) are all later but it would be foolish to rule it out in the 1st Century. There was no canon - no official list of sacred texts - but there does seems to have been a large measure of agreement over most of the books. The Greek and Hebrew versions of books were often significantly different; the Septuagint, as it's called, wasn't a translation so much as an independent textual tradition which was in use in the Diaspora.
The Jews decided on their canon in the same period as the
church picked out the NT canon, but the Septuagint contained a
good deal of material which doesn't exist in Hebrew; either it was written in Greek, or the Hebrew version was left out of the canon and eventually lost. Since the
church was largely Greek-speaking, they used the Septuagint, as the Orthodox churches do to this day. The Ethiopian Orthodox
Church adds 1 Enoch, which is quoted in the NT, but nobody else includes it.
Around the 3rd Century, possibly due to
Christian use of the Septuagint, the Jews decided to use the Hebrew canon rather than the Greek. The
church in the Eastern Empire, which was obviously Greek-speaking, carried on using in, while in the
West, Jerome translated the Hebrew, and produced the first Latin Bible. That left the books which are left out in the Hebrew in limbo as far as the Western
Church was concerned. Known as the Apocrypha, they stayed in limbo till the Reformation.
The Reformers decided they weren't canonical, on the dubious grounds that Jesus never quoted them. So the Council of Trent, inevitably, decided to include it in the Catholic Bible. So a Protestant Old Testament is strictly limited to the Hebrew books, and is shorter than anyone else's. The Catholic version adds some books and parts of books taken from he Greek, while
still using the Hebrew elsewhere. The Orthodox Churches use the Greek version throughout, and the Ethiopian Orthodox add 1 Enoch. When people start talking about 'the Bible' the first question should be, 'Whose Bible?'