Can You Rank These Valid Mysqli Executions ?

Hiya,

Which of these IF CONDITION codes are valid ?
And can you rank the valid ones according to your choice by giving reasons to your choices ?

Thanks!

$conn = mysqli_connect("localhost","root","","buzz");

$sql = "INSERT into users (username,email) VALUES (?,?)";

if($stmt = mysqli_prepare($conn,$sql))
{
    mysqli_stmt_bind_param($stmt,"ss",$_POST[username'],$_POST['email']);

    if(!mysqli_stmt_execute($stmt)) //FIRST CHOICE

        if(mysqli_stmt_execute($stmt)==FALSE) //IS THIS VALID ? RECKON VALID. SECOND CHOICE
    if(mysqli_stmt_execute($stmt)===FALSE) //IS THIS VALID ? RECKON VALID. BUT POINTLESS.

        if(mysqli_stmt_execute($stmt)!=TRUE) //IS THIS VALID ? 5TH CHOICE
        if(!mysqli_stmt_execute($stmt)!==TRUE) //IS THIS VALID ? RECKON VALID. BUT POINTLESS.

        if(mysqli_stmt_execute($stmt)==NULL) //IS THIS VALID ?
    if(!mysqli_stmt_execute($stmt)===NULL) //IS THIS VALID ?

        if(mysqli_stmt_execute($stmt)==0) //IS THIS VALID ? RECKON INVALID.
    if(!mysqli_stmt_execute($stmt)===0) //IS THIS VALID ? RECKON INVALID.

        if(mysqli_stmt_execute($stmt)<1) //IS THIS VALID ?

    if(mysqli_stmt_execute($stmt)!=1) //IS THIS VALID ?
        if(mysqli_stmt_execute($stmt)!==1) //IS THIS VALID ?

        {
        echo 'Something went wrong! Please notify webmaster following error!';
                die('Error 2!');
    }
    else
    {
        die('Thank you for your submission!)';
    }
}
else
{
    echo 'Something went wrong! Please notify webmaster following error!';
        die('Error 1!');
}

Q1: Which of my choices are incorrect and why ?
Q2. Out of the valid IF CONDITIONS, can you rank them according to most valid on top and least valid on bottom ? This should teach me best practice.