Moves node to back of list. Moves node to front of list. It can be a new node, or it can be an existing node. Moves node to back of list. It can be a new node, or it can be an existing node.
Removes node if it's in list.
Does nothing if it's not. When a node is removed, both its links are set to null. Obtain the backmost node, and remove it from list too. Get the next node of this list. The next node, or null if this one was last.