在C中未知标题指针位置时，在单个链接列表中插入节点

Actually, we have a two pointers in a single link list. The head pointer position is unknown. The second pointer is known. For example, Consider this is a list 1->2->3->4->5. The second pointer is pointing the element 2. If we try to insert the node at position 2 between node1 and 2, how the insertion take place?. Is it possible to insert the node as same?Actually, we have a two pointers in a single li