Difference Between /Dev/Input/Mouse0 and /Dev/Input/Mice

I'm working with a mouse USB driver and I really don't know how to difference and use information send by /dev/input/mouse0 and /dev/input/mice

After few search on Google, I've found a few code about using /dev/input/mice

int fd, bytes;
unsigned char data[4];

const char *pDevice = "/dev/input/mice";

// Open Mouse
fd = open(pDevice, O_RDWR);
if(fd == -1)
{
    printf("ERROR Opening %s\n", pDevice);
    return -1;
}

int left, middle, right;
signed char x, y;

// Read Mouse
bytes = read(fd, data, sizeof(data));

if(bytes > 0)
{
    left = data[0] & 0x1;
    right = data[0] & 0x2;
    middle = data[0] & 0x4;

    x = data[1];
    y = data[2];
    printf("x=%d, y=%d, left=%d, middle=%d, right=%d\n", x, y, left, middle, right);

    if(left)
        return left;
    if(right)
        return right;
    if(middle)
        return middle;
}

return 0;

This program works but didn't get any information about the wheel scroll

I was able to found a program which use /dev/input/event0

int fd;
struct input_event ev
const char* pFile = "/dev/input/event0";

fd = open(pFile, O_RDONLY);
if(fd == -1)
{
    printf("ERROR Opening %s\n", pFile);
    return -1;
}

read(fd, &ev, sizeof(ev));
std::cout << "type : " << ev.type << "  code : " << ev.code << "  value : " << ev.value << std::endl;

close(fd);

return 0;

But there is a problem for diagonal movement because this file saved only 1 coordinate at same time, and X coordinate have priority on Y; so it's pretty annoying when you want to move your mouse on Y axis

However, I don't find any code to use /dev/input/mouse0, so what information are saved in this file?

So my questions are : 1. What information are saved in /dev/input/mouse0? 2. How can I read all mouse information without opening 2 files, and without priority problem (whell scrolling + X/Y axis movement)?