Can someone explain why DEFG was correct or wrong? It is C++

Which of the following descriptions are TRUE about Linked List? (((F)(G) the Big-0 complexity to insert a node into a singly linked list is always 0(1). The Big-0 complexity to delete a node from a doubly linked list is always 0(1). If there are both head and tail pointers in doubly linked list, then the insertion and deletion operation is always 0(1) at the beginning and end of the list. If a stack is implemented using a singly linked list, then it is more efficient to use the head pointer as the top of the stack. If a queue is implemented using a singly linked list (with tail pointer), then it is more efficient to use the tail pointer as the front of the queue and the head pointer as the rear of the queue than vice versa. Given only a pointer pointing to one of the nodes to be deleted, it is more efficient to delete that node in a doubly linked list than in a singly linked list. Merging two sorted linked lists, each with N nodes, is 0(N)