insertion in Linked list

#include <stdio.h>
#include <stdlib.h>

struct Node{
    int data;
    struct Node* next;
};

void linkedListTraversal(struct Node *ptr)
{
    while (ptr!=NULL)
    {
        printf("Element: %d\n", ptr->data);
        ptr = ptr->next;
    }
}

//Case 1
struct Node * insertAtFirst(struct Node *head , int data){
    struct Node *ptr = (struct Node *)malloc(sizeof(struct Node));
    ptr->data=data;
    
    ptr->next=head;
    return ptr;
}
//Case 2
struct Node * insertAtIndex(struct Node *head, int data, int index){
    struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
    struct Node * p = head;
    int i = 0;
    
    while (i!= index-1)
    {
        p = p->next;
        i++;
        
    }
    ptr->data= data;
    ptr->next = p-> next;
    p->next= ptr;
    return head;
}

// case 3
struct Node * insertAtEnd(struct Node *head, int data){
    struct Node * ptr = (struct Node *) malloc(sizeof(struct Node));
    ptr->data = data;
    struct Node *p = head;
    
    while(p-> next !=NULL){
        p = p->next;
    }
    p->next = ptr;
    ptr->next = NULL;
    return head;
}
    
//Case 4
struct Node * insertAfterNode(struct Node * head, struct Node *prevNode, int data){
    struct Node *ptr = (struct Node *)malloc(sizeof(struct Node));
    ptr->data = data;
    ptr->next=prevNode->next;
    prevNode->next= ptr;
    
    return head;
}
    

int main() {
    struct Node *head;
    struct Node *second;
    struct Node *third;
    struct Node *fourth;
    
    head=(struct Node *)malloc(sizeof(struct Node));
    second=(struct Node *)malloc(sizeof(struct Node));
    third=(struct Node *)malloc(sizeof(struct Node));
    fourth=(struct Node *)malloc(sizeof(struct Node));
    
    head->data= 7 ;
    head->next= second;
   
   second->data= 11;
   second->next = third;
   
   third->data= 41;
   third->next = fourth;
   
   fourth->data= 66;
   fourth->next = NULL;
   
   printf(" lInked before insertion\n");
   linkedListTraversal(head);
   
   head = insertAfterNode(head, third, 45);
   printf("\nLinked list after insertion\n");
   linkedListTraversal(head);
   
   return 0;
}