Good, it's a fresh example...okay..so we have a Set and a LinkedList. On a parent data structure, if we have got a 'set' now, it means we have changed the data structure and possibly eliminated the duplicate ones to get a 'Set'. To get a linkedlist, we have changed the data structure to get a list(ordered coll) and then added extra fucntions like getting elements from end or begining. 'Set' here will just be an inheritance example. To some extent, linkedlist can be called decorator if u consider a LinkedList class typed over a list interface. But remember its still a static inheritance, so not a very good case for decorator. This is just my opinion and i respect ur right to disagree.
2)Both Structural and behavioral patterns can be static or dynamic. Decorator is still structural bcz we are not changing the behaviour of obj at run-time, we r giving it some extra responsiblity to do. So we say that the structure of object is changed to suit the extra responsibilities.e.g may be we have to add an internal buffer with the object to support buffering...still a structural pattern.
In chain of resp, we say that whichever obj want to be a part of this chain, it needs to implement some func ..and so if CONDITION IS MET..it
will have the responsibility to trap the request. So whenever some communication between objects is there, its a healthy indicator of behavioral pattern. 'request' being comm obj in this case.