Question on priority queue and linked lists

[hopesfall]

So I'm studying for my final and I've answered about 30 of the 40 review questions but I'm having trouble on two of them:

1.Explain why, counter-intuitively, a Priority Queue ADT cannot be implemented by wrapping around a Queue ADT, nor vice-versa.

2.Distinguish between a deep copy and a shallow copy of a linked list. How are they different in their implementation? In what situations would you want one or the other?

I don't really know how to answer #1 at all and for #2, I know what the difference between a deep copy and a shallow copy is but I'm not sure in what situations I would want to use one over the other...

Can anyone please help? Thanks