1) This is a modify Information button to bring them back to the checkout page and a link to view the cart to bring them back to the cart page.
you could show the side menu on the confirm page, by editing line 3:
$blockSideMenu = true;
//$blockSideMenu = true;
2) In the Power store settings, go to the Store email settings and enter your email for the Receipt Email CC or Receipt Email BCC setting.
3) No, the cart will not show any shipping if the total is 0, this is not supported.