I'm creating an extremely challenging regex problem that combines multiple pattern types with subtle valid/invalid distinctions. This challenge requires advanced techniques like lookaheads/lookbehinds, non-capturing groups, balanced delimiters, and precise boundary matching. The text contains multiple format categories including:

1. Various datetime formats (ISO 8601, regional formats with different separators)
2. Network addresses (IPv4/IPv6)
3. Complex email addresses with special characters
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