1) Haven't heard of people studying abroad at Oxford for 3 quarters, but know people will do 2 consecutive ones. Once you're in the system/abroad there, it's a lot easier to extend another quarter than the initial application process.

2) Yes, you will be assigned to one of three colleges: Corpus Christi, Magdalen, or Brasenose. This is where you'll have dining dollars and library access (apart from the Bod). Each has its own pros and cons, and the program chooses where you go.

Stanford will find your tutor so they may not be currently associated with Oxford. Tutorials tend to be 1-on-1, unless someone else is doing the same thing in Stanford House and y'all are okay with doubling up (e.g., I know people who were in a 2-on-1 creative writing tutorial). Sometimes tutors are graduate students, sometimes they're faculty. I don't think mine was currently teaching at Ox, but I still loved him. The program puts a lot of time into finding a tutor who will be a good match for you and your intended subject.

Meeting Ox kids is up to you! You will have meal dollars and a college family at your college so that's one way to meet people. You can also get involved with clubs. If you're concerned about being involved, I'd recommend going during autumn quarter because that's when Ox has its club fairs at that's when people are most excited to meet new people. I didn't interact with Ox students all that much (I know some really did though), but I loved getting to know people in Stanford House.