Re: Previous 9 tails jinchuriki
Odds are, Hashirama kept the Kyuubi for Konoha, partially because both he (the Senju) and Madara (the Uchiha) could control it. He never put it into a Jinchuuriki because he and Madara couldn't USE it effectively in a Jinchuuriki. After he died, since they had no way to control the Kyuubi, no obvious candidate for being the Jinchuuriki, and no real desire to build up military power, the Kyuubi was never sealed into a jinchuuriki.
There's been absolutely no indication that there ever was a previous Kyuubi jinchuuriki, and there's been a fair amount of indication that there never was one.
I am a leaf on the wind. Watch how I soar.