I'm creating an extremely difficult challenge that pushes regex experts to their limits. The challenge includes a mix of complex email addresses featuring '+' signs, dots, hyphenated subdomains and unusual characters; multiple phone number formats with international codes, parentheses, dashes, and even an extension part; dates provided in three different formats with varied separators; symmetric product codes that ideally require backreferences to ensure the prefix matches the suffix; and a stan... (truncated)