Im guessing you guys weren't at the info day today. It varies, some councils are taking on two. It depends really. Some of the eastern regions are only doing the one, yet most of the London Boroughs are doing between 2 and 4 placements.
But Avituss I will answer your questions in the following:
1. If you pass the interview stage, you CANNOT defer. The Councils will want you start the following October. If you were rejected (I prefer the term unlucky personally...) then you CAN defer straight to the interview stage.
2. As above.