Can I create a private calendar appointment with an iPhone?

If I understand correctly, the other student took the class after you took it, so it's clear that she cheated from you, not vice versa. I suspect they merely want to talk to you to find out exactly what happened. You are probably not in any trouble, unless there is a school policy against sharing old assignments, or the professor asked students not to do this, or you knew that she would have the same assignment when she took the class. So I would simply answer any questions they have, and explain why you did what you did.

drupal_goto() will use $_GET['destination'] when it is set. The following is the code used from the function.

  if (isset($_GET['destination']) && !url_is_external($_GET['destination'])) {
    $destination = drupal_parse_url($_GET['destination']);
    $path = $destination['path'];
    $options['query'] = $destination['query'];
    $options['fragment'] = $destination['fragment'];
  }

Setting $edit['redirect'] inside hook_user_login() doesn't have any effect.
What you can do is changing $_GET['destination'] in hook_user_login(). If you want to be sure the user is redirected to the path you set, you should be sure your hook is executed last, for example by increasing the weight of your module.

Ah, you had me confused there for a while. Stick \begingroup before the push and \endgroup before the pop.

the idea is that you locally redefine the footnote commands to save their contents but the code assumes that by the time you execute the saved commands they have their normal meanings back, otherwise they just save their contents again.

Note though that lifting the footnotes out of the floating table is inherently fragile, if the table floats off to another page, the footnotes will not float with it, and if it ends on a p float page, LaTeX does not support footnotes on such a page.