Insert, Delete in Linked List

#include<iostream>
#include<cstdlib>
#include<string>
using namespace std;

struct node{
    int x;
    struct node* next;
};

struct node* create_new_node(){
    struct node* tmp;
    tmp = new node;
    return tmp;
};

void print_list(struct node* h){
    struct node* it; //iterator for iterating the whole list;
    it=h; // start from head
    cout<<"List: ";
    while(it != NULL){
        cout<<it->x<<" "; // why it->x is used here instead of it.x?
        it = it->next;
    }
    cout<<endl; //new line
}

struct node* list_insert_first(struct node* h, int value){
    struct node* temp;
    temp = create_new_node();
    temp->x = value; // why temp->x is used here instead of temp.x?
    temp->next = h; // because insert-first here
    h = temp; //why this should be done? check this!!
    return h;
}

struct node* list_insert_last(struct node* h, int value){
    struct node* temp;
    struct node* it;
    temp = create_new_node();
    temp->x = value; // why temp->x is used here instead of temp.x?
    temp->next = NULL;
    if(h==NULL) {
        return temp; //why?
    }
    it = h; //starting to iterate from head
    while(it->next!=NULL){ //iterating till the last node
        it = it->next;
    }
    it->next = temp; //inserting last node
    return h;
}

struct node* list_delete_last(struct node* h){
    if(h==NULL) return h; // check why I did this?
    else if(h->next == NULL) return NULL; // check why I did this? ***
    struct node* it = h->next; // interesting!! instead of initializing it by head, I initialized it by head->next. Why? ***
    struct node* it_1 = h; // What is the role of this iterator?
    while(it->next!=NULL){
        it_1 = it;
        it = it->next;
    }
    it_1->next = NULL; // Why I initialized it_1->next by NULL? ***
    return h;
}

struct node* list_delete_first(struct node* h){
    if(h==NULL) return h;
    else{
        return h->next; // interesting!! why? ***
    }
}

int main(){
    struct node* head; //starting node of the list
    head = NULL; // at first no value, so nothing in that node(you must initialize head before comparing it!!)

    string s;
    int value;
    while(1){
        cin>>s;
        if(s=="insert-first"){
            cin>>value;
            head = list_insert_first(head, value);
        }
        else if(s=="insert-last"){
            cin>>value;
            head = list_insert_last(head, value);
        }
        else if(s=="delete-last"){
            head = list_delete_last(head);
        }
        else if(s=="delete-first"){
            head = list_delete_first(head);
        }
        else if(s=="exit"){
            break;
        }
        else{
            cout<<"Operation is not identified!"<<endl;
        }
        print_list(head);
    }

}

/*
input:
insert-first 1
insert-first 3
insert-last 2
insert-last 4
insert-first 5
insert-last 6
insert-first 8
insert-last 7
insert-first 1
insert-last 9
insert-last 10
insert-first 11
delete-last
delete-last
delete-first
delete-first
delete-first
delete-last
delete-first
delete-last
delete-first
delete-first
delete-last
delete-last
delete-first
delete-last
delete-first
insert-first 1
exit
*/

/*
output:
List: 1
List: 3 1
List: 3 1 2
List: 3 1 2 4
List: 5 3 1 2 4
List: 5 3 1 2 4 6
List: 8 5 3 1 2 4 6
List: 8 5 3 1 2 4 6 7
List: 1 8 5 3 1 2 4 6 7
List: 1 8 5 3 1 2 4 6 7 9
List: 1 8 5 3 1 2 4 6 7 9 10
List: 11 1 8 5 3 1 2 4 6 7 9 10
List: 11 1 8 5 3 1 2 4 6 7 9
List: 11 1 8 5 3 1 2 4 6 7
List: 1 8 5 3 1 2 4 6 7
List: 8 5 3 1 2 4 6 7
List: 5 3 1 2 4 6 7
List: 5 3 1 2 4 6
List: 3 1 2 4 6
List: 3 1 2 4
List: 1 2 4
List: 2 4
List: 2
List:
List:
List:
List:
List: 1
*/