why there's so many versions of c++ Hello World code and

There aren't that many. Correct are ones that output message similar to "Hello world!" to stdout.

If a piece of code does what it's supposed to do and it compiles, it's correct, you dumb shit.

>>55934136
Uh OP...that's C. And that's not even the standard. As of C89, it is no longer necessary to return an int as the compiler does that implicitly.

>>55934177
How does that make it not standard?

>>55934177
That has nothing to do with the standard, that's simply an implementation detail of the compiler.

The only correct ones are

#include<stdio.h>

int main(void)
{
    puts("Hello world!\n");
    return 0;
}

and

#include<iostream>

int main(void)
{
    using namespace std;
    cout << "Hello world!" << endl;
    return 0;
}

>>55934224
Why correct using void into main parameter?

>>55934224
>puts and a \n
bruh...

>>55934364
'tism

>>55934136
Some are written in ways to save memory space.

>>55934400

#include <iostream>
#include <vector>

int main()
{
    char* s = "hello, world\n";
    vector<char> v = new vector<char>(s, s + sizeof(s) / sizeof(char));
    for (char *pc = v.begin(); pc < v.end(); pc++)
        cout << *pc;
    delete v;
}

>>55934577
*std::cout
*s + sizeof(s) / sizeof(char) - 1 (for null termination)