[SDL C++] How do I remove an applied surface?

[Smoking Bros]

Hello everyone!
I'm working on a little 2D Game, and I managed to make a 32x32 fill out my whole window :) and I also managed to override the whole 32x32 grass terrain with a 40x40 desert/sand terrain. But I can't figure out how to remove the images I applied on the grass surface.. 'SDL_FreeSurface(######);' just exists the program..
Here's my complete source code:

#include "SDL/SDL_2D.h"

int main(int argc, char * argv[])
{
    if(!init())
    {
        return 1;
    }

	sprite.x = 150;
	sprite.y = 150;
	src.x = 128;
	src.y = 0;
	src.w = SPRITE_SIZE;
	src.h = SPRITE_SIZE;
	
	while(!game_over)
	{
		SDL_Event event;
		
		if(SDL_PollEvent(& event))
        {
			handle_event(event);
		}

		if(sprite.x <= 0)
		    sprite.x = 0;
		if(sprite.x >= SCREEN_WIDTH - SPRITE_SIZE) 
			sprite.x = SCREEN_WIDTH - SPRITE_SIZE;
		if(sprite.y <= 0)
			sprite.y = 0;
		if(sprite.y >= SCREEN_HEIGHT - SPRITE_SIZE) 
			sprite.y = SCREEN_HEIGHT - SPRITE_SIZE;
			
		for(int x = 0; x < SCREEN_WIDTH / SPRITE_SIZE; x++) 
        {
			for(int y = 0; y < SCREEN_HEIGHT / SPRITE_SIZE; y++)
            {
				grass.x = x * SPRITE_SIZE;
				grass.y = y * SPRITE_SIZE;
				apply_grass(grass_area, screen);
                			
				if(check_for_collision())
				{
                    sand.x = x * SPRITE_SIZE;
                    sand.y = y * SPRITE_SIZE;
                    apply_sand(desert_area, grass_area);
                }
			}
		}
		
		apply_sprites(sprites, screen);
		apply_object_01(230, 190, teapot, screen);
		apply_go_to_message(10, 10, go_to, screen);
		
		if(SDL_Flip(screen) != 0)
		{
            return 1;
        }
	}
}

#include <iostream>
#include "SDL.h"

#define SCREEN_WIDTH  640
#define SCREEN_HEIGHT 450
#define SPRITE_SIZE 32
using namespace std;
void handle_event(SDL_Event event);
bool init();
bool load_files();
SDL_Surface * load_image(string file);
SDL_Surface * load_color_keying(string file);
void apply_sprites(SDL_Surface * source, SDL_Surface * dest);
void apply_grass(SDL_Surface * source, SDL_Surface * dest);
void apply_object_01(int x, int y, SDL_Surface * source, SDL_Surface * dest);
bool check_for_collision();
void apply_go_to_message(int x, int y, SDL_Surface * source, SDL_Surface * dest);
void apply_object_02(int x, int y, SDL_Surface * source, SDL_Surface * dest);
void apply_sand(SDL_Surface * source, SDL_Surface * dest);

bool game_over = false;
int color_key;
SDL_Rect src, sprite, grass, object_01, message_01, object_02, sand;
SDL_Surface * screen, * sprites, * grass_area, * teapot, * go_to,
            * teapot_2, * desert_area;

void handle_event(SDL_Event event)
{
	switch(event.type)
    {
		case SDL_QUIT:
			game_over = true;
		break;
		case SDL_KEYDOWN:
			switch(event.key.keysym.sym)
            {
			    case SDLK_ESCAPE:
				case SDLK_q:
					game_over = 1;
				break;
				case SDLK_LEFT:
					if(src.x == 192)
						src.x = 224;
					else
						src.x = 192;
					    sprite.x -= 5;
				break;
				case SDLK_RIGHT:
					if(src.x == 64)
						src.x = 96;
					else
						src.x = 64;
					    sprite.x += 5;
				break;
				case SDLK_UP:
					if(src.x == 0)
						src.x = 32;
					else
						src.x = 0;
					    sprite.y -= 5;
				break;
				case SDLK_DOWN:
					if(src.x == 128)
						src.x = 160;
					else
						src.x = 128;
					    sprite.y += 5;
				break;
			}
		break;
	}
}

bool init()
{
    if(SDL_Init(SDL_INIT_EVERYTHING) != 0)
	{
	    return false;
	}
	
	SDL_WM_SetCaption("2D Game", NULL);
	screen = SDL_SetVideoMode(SCREEN_WIDTH, SCREEN_HEIGHT, SPRITE_SIZE, SDL_SWSURFACE);
	SDL_EnableKeyRepeat(70, 70);
	
	if(!load_files())
	{
	    return false;
	}
	
	return true;
}

bool load_files()
{
	sprites = load_color_keying("GFX/sprite.bmp");
	grass_area = load_image("GFX/grass.bmp");
	teapot = load_color_keying("GFX/teapot.bmp");
	go_to = load_color_keying("GFX/enter_teapot.bmp");
	teapot_2 = load_color_keying("GFX/teapot_2.bmp");
	desert_area = load_image("GFX/desert.bmp");
	
	if(sprites == NULL)
	{
	    return false;
	}
	if(grass_area == NULL)
	{
	    return false;
	}
	if(teapot == NULL)
	{
	    return false;
	}
	if(go_to == NULL)
	{
	    return false;
	}
	if(teapot_2 == NULL)
	{
	    return false;
	}
	if(desert_area == NULL)
	{
        return false;
    }
	
	return true;
}

SDL_Surface * load_image(string file)
{
    SDL_Surface * loaded_image = NULL;
    SDL_Surface * optimized_image = NULL;
	
    loaded_image = SDL_LoadBMP(file.c_str());
	
    if(loaded_image != NULL)
    {
        optimized_image = SDL_DisplayFormat(loaded_image);
        SDL_FreeSurface(loaded_image);
    }
	
    return optimized_image;
}

SDL_Surface * load_color_keying(string file)
{
    SDL_Surface * loaded_image = NULL;
    SDL_Surface * optimized_image = NULL;

    loaded_image = IMG_Load(file.c_str());

    if(loaded_image != NULL)
    {
        optimized_image = SDL_DisplayFormat(loaded_image);
        SDL_FreeSurface(loaded_image);

        if(optimized_image != NULL)
        {
            Uint32 color_key = SDL_MapRGB(optimized_image->format, 0, 0xFF, 0xFF);
            SDL_SetColorKey(optimized_image, SDL_SRCCOLORKEY, color_key);
        }
    }

    return optimized_image;
}

void apply_sprites(SDL_Surface * source, SDL_Surface * dest)
{
    SDL_BlitSurface(source, & src, dest, & sprite);
}

void apply_grass(SDL_Surface * source, SDL_Surface * dest)
{
    SDL_BlitSurface(source, NULL, dest, & grass);
}

void apply_object_01(int x, int y, SDL_Surface * source, SDL_Surface * dest)
{
    object_01.x = x;
	object_01.y = y;
	
	SDL_BlitSurface(source, NULL, dest, & object_01);
}

bool check_for_collision()
{
    if(sprite.x > 470 + 5 && sprite.y > 320 + 5)
	{
	    return true;
	}
	
    return false;
}

void apply_go_to_message(int x, int y, SDL_Surface * source, SDL_Surface * dest)
{
    message_01.x = x;
	message_01.y = y;
	
	SDL_BlitSurface(source, NULL, dest, & message_01);
}

void apply_object_02(int x, int y, SDL_Surface * source, SDL_Surface * dest)
{
    object_02.x = x;
	object_02.y = y;
	
	SDL_BlitSurface(source, NULL, dest, & object_02);
}

void apply_sand(SDL_Surface * source, SDL_Surface * dest)
{
    SDL_BlitSurface(source, NULL, dest, & sand);
}

Please help me?..

[Smoking Bros]

forget it, I fixed it myself, by setting a boolean I just created (remove_objects) to true and therefore setting 'teapot' and 'go_to' to a x & y posistion that're out of the screen :D