Why does a function which returns void not hold value?

Question

I think I'm missing something important about pointers and memory. This is the minimum code needed:

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

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


struct node* init(int value) {
    struct node* head = (struct node*)malloc(sizeof(struct node));
    if (!head) return NULL;
    head->value = value;
    head->next = NULL;
    return head;
}

void insert_back(struct node* head, int value) {
    if (!head) return;
    struct node* temp = head;
    struct node* new = (struct node*)malloc(sizeof(struct node));
    while (temp->next != NULL) {
        temp = temp->next;
    }
    temp->next = new;
    new->value = value;
    new->next = NULL;
    return;
}

struct node* insert_front(struct node* head, int value) {
    struct node* temp;
    struct node* new = (struct node*)malloc(sizeof(struct node));
    new->value = value;
    new->next = head;
    temp = head;
    head = new;
    head->next = temp;
    return new;
}

void insert_front_2(struct node* head, int value) {
    struct node* temp;
    struct node* new = (struct node*)malloc(sizeof(struct node));

    new->value = value;
    new->next = head;

    temp = head;

    head = new;
    head->next = temp;
}

void print_list(struct node* head) {
    if (!head) return;

    struct node* temp = head;
    int i = 0;
    while (temp != NULL) {
        printf("At position %d value %d \n", i, temp->value);
        i++;
        temp = temp->next;
    }
}

int main() {
   struct node* head = init(5);
    insert_back(head, 7);
    insert_back(head, 9);
    insert_back(head, 12);
    insert_back(head, 13);
    insert_back(head, 14);
    insert_back(head, 15);

    head = insert_front(head, 100);
    insert_front_2(head, 200);
    print_list(head);
    free(head);
    return 1;
}

The problem concerns the function void insert_front_2(...). I do not understand why struct ndoe * instert_front works perfectly, but insert_front_2 does not hold the new head once I am in the main - that is, when I print the list, the new head is not printed. Any ideas? How should I modify void insert_front_2(...) to make it work?