Board Thread:Questions and Answers/@comment-4161952-20130522233943/@comment-6553047-20130523031759

1: We do not know. However, as stated by Yamamoto, they can not exploit its power fully.

2: According to Yamamoto (the only one that seems to know much about them), they need to fully analyze the Bankai and its power before eing able to steal it. That would most certainly include the techniques of the Bankai.

3: We've only seen them being able to steal one at a time. I compare it to how an Asauchi can only become one Zanpakutou. Because it can only house one Zanpakutou Spirit at a time. (though I may be wrong on that one)