Answer 1

You have misunderstood the concept the procedure should be inside the function

#include <iostream>
using namespace std;

int timesTwo(int x) {
return x*2;
}

int main() {
cout << timesTwo(8) << endl;
return 0;
}

Answer 2

Actually tere are two types of this
1. Functions
2. Sub Routine

FUNCTION
It takes an input and gives a output after processing the input

SUB ROUTINE
It takes an Input and do something but do not return any thing.

In c++ Defining Function and Sub Routines are same}
If you do not want to return anything follow this template

void function-name(parameters){...}

Answer 3

It's not necessary that a function returns only int
It depends on its defination

General template of function

Data-Type Function-name(parameter){
...
}

data -type defines which type is returned by function
void means it do not return anything