The way I see it, "money" is just a trade medium - something to pass back and forth while getting what you actually want via the act of trading. That said, the concept of money is pretty much guaranteed to exist in one way or another as long as trade is required.
Being in a post-scarcity society is by no means saying that trade is no longer required. I would guess that two conditions must be met for trade to become obsolete:
- Every single human being/ cluster of humans is entirely self-sufficient;
- No single person/ cluster of people has an excess of any resource.
This is nigh-impossible, simply because it is extremely inefficient for every human to be equipped with all the necessary tools and knowledge for survival on their own. The structure of today's world allows each person to acquire something they lack from someone else who is producing an excess, and money is just there to provide the medium. Technology is not an answer, because unless every person is able to produce that technology (e.g. a magic box) on their own without any external supplies or training, you will still have to trade for you to acquire your own box.
Since my answer is that such a change is highly improbable, I hope you don't mind that I not answer the other two parts of your question.