doubly linked list, most functions (updated)

#include <iostream>
using namespace std;

class Node {
    public:
    int data;
    Node* prev;
    Node* next;
};

Node* head = new Node();
Node* tail = new Node();


void insertAtBeginning(Node* head, int data) {
        Node* temp = new Node; 
        temp->prev = NULL;
        head->next = temp;
        temp->data = data;
        temp->next = NULL;
        
        tail->prev = temp;
}

void insertAtEnd(Node* tail, int data) {
    Node* temp = new Node();
    temp->data = data;
    Node* last = tail->prev;
    
    temp->prev = last;
    last->next = temp;
    
    tail->prev = temp;
    temp->next = NULL;
    
}

void insertAtPosition(Node* head, int data, int pos) {
    Node* temp = new Node();
    temp->data = data;
    Node* current = head->next;
    int i = 1;
    
    if(head->next == NULL) {
        insertAtBeginning(head, data);
    }
    else {
    
    while(i < pos && current->next != NULL) {
        current = current->next;
        i++; 
    }
    
    if(current->next == NULL) {
        insertAtEnd(tail, data);
    }
    
    else {
    
    Node* next = current->next;
    temp->next = next;
    temp->prev = current;
    
    next->prev = temp;
        }
    }
}

void deleteAtBeginning(Node* head) {
    if(head->next == NULL) {cout << "cannot delete." << endl; return;}
    Node* first = head->next;
    Node* second = first->next;
    
    head->next = second;
    second->prev = NULL;
    
    free(first);
}

void deleteAtEnd(Node* tail) {
    if(tail->prev == NULL) {cout << "cannot  delete ."  << endl; return;}
    Node* last = tail->prev;
    Node* secondlast = last->prev;
    
    tail->prev = secondlast;
    secondlast->next = NULL;
    
    free(last);
}

void deleteAtPosition(Node* head, int pos) {
    if(head->next == NULL) {cout << "cannot delete." << endl; return;}
    
    else {
    Node* current = head->next;
    Node* temp = new Node();
    Node* next = new Node();
    
    int i = 1;
    while(i < pos && current->next != NULL) {
        current = current->next;
        i++;
    }
    
    if(current->next == NULL) {
        deleteAtEnd(tail);
        } else {
            temp = current->next;
            next = temp->next;
            
            current->next = temp->next;
            next->prev = temp->prev;
            
            free(temp);
        }
    }
}

void displayBack(Node* tail) {
    Node* current = tail->prev;
    
    while(current != NULL) {
        cout << current->data << endl;
        current = current->prev;
    }
}

void displayForward(Node* head) {
    Node* current = head->next;
    while(current != NULL) {
        cout << current->data << endl;
        current = current->next;
    }
}

int main() {
    insertAtBeginning(head, 1);
    insertAtEnd(tail, 3);
    insertAtEnd(tail, 5);
    insertAtPosition(head, 7,1);
    insertAtEnd(tail, 2);
    insertAtEnd(tail, 20);
    deleteAtPosition(head, 1);
    displayBack(tail);
    
    return 0;
}