Question about Card ShortLink pattern

Recently I managed to request a card by a short identifier. I would like to clarify a few points:

  1. For a card id, there is a pattern in the documentation that it must match. Is there any pattern for shortlink?
  2. Is there any other identifier, besides card id and shortlink, by which possible to get a card? And if there is, can you please also specify a pattern for it?