A BC Septuagint?

What evidence is there:

1. for a B.C. Septuagint?
2. that a B.C. Septuagint was widely accepted and used?
3. that B.C. Septuagint was commonly accepted and used by Jews?
4. that Jews would adopt pagan greek (used for commerce) for their religious studies and practices?
5. that if there was a septuagint as described in pseudepigrapha letter of Aristeas, that it was more than the Pentateuch?

Also:

1. Of the many variants of so-called septuagints, which is the authentic one?
2. Of the so-called septuagint texts we have today, which one is based on mss that are older than codexes Alexandrinus, Vaticanus, and Sinaiticus?