Hi,
You can add a return URL in the payment method by adding the code:
'return_url' => array('RETURN_URL', 'input'),
after the line:
'debug' => array('DEBUG', 'boolean','0'),
in the file plugins/hikashoppayment/epay/epay.php and then editing the payment method in the backend.
If that's not what you're talking about, please explain better what you want.
Regarding the emails, you can't create yourself new emails. However, you can modify the order status notification via the menu System>Emails so that it would display different things base on the order status with simple PHP:
<?php if($data->order_status=="confirmed){
echo "something";
}else{
echo "something else";
} ?>