A few questions on classes!..

Hello!
I just recently registred at this forum and I must say it seems to be a nice and friendly place!
I'm currently studying a beginners course in C++ and I'm a bit stuck right now.. So I thought perhaps it might be a good idea to ask soem questions here and see if any of you guys could help me out!

My problems are the following..

1. I'm making a program with a default constructor and an overloaded constructor. They're both called by different rules and produces a testline of text when called. The assignment is to give the overloaded constructor default arguments to see what happens. I wonder, what is a default argument i an overloaded constructor?

2. How do you instance an object from a class in different scope?

3. How do you send an object "by value" to a function?

4. Here's a "Non class" question.
How do you make a function which swaps the values of two indexes on a vector (like swaps numbers[1] with numbers[2])?
I've tried to make this but it only works when showing the results of the swap in the function, not when I show the results in the main function. When doing that it remains unchanged.
Here's the code I've used. What am I doing wrong?

Code:

#include <iostream>
#include <vector>
using namespace std;

int swap_values(vector<int>numbers);

int main ()
{
     vector<int>numbers(3);
    cout << "Let's swap vector values\n";
    cout << "Enter value 1 " << endl;
    cin >> numbers[1];
    cout << "Enter value 2 " << endl;
    cin >> numbers[2];

    cout << "vector 1: " << numbers[1] << endl;
    cout << "vector 2: " << numbers[2] << endl;
    cout << "vector 3: " << numbers[3] << endl;
    swap_values(numbers);
    cout << "vector 1: " << numbers[1] << endl;
    cout << "vector 2: " << numbers[2] << endl;
    cout << "vector 3: " << numbers[3] << endl;      
    cin.get();
    cin.get();
    return 0;
}



int swap_values(vector<int>numbers)
{
    
    numbers[3] = numbers[1];
    numbers[1] = numbers[2];
    numbers[2] = numbers[3];
    return 1;
}

Thanks a lot for helping me! It means a lot!


Simon