Which condition is typically used to determine the end of the list during standard traversal of a singly linked list?

What is the worst-case time complexity of inserting 'n' elements into an initially empty linked list such that the linked list remains sorted?

What are the contents of an initially empty stack (from bottom to top) after performing the following operations? PUSH(A); PUSH(B); PUSH(C); POP; PUSH(D); POP; POP; PUSH(E); PUSH(F); POP;