How did a 'guess paper' leak trigger NEET UG 2026 controversy?

NTA has cancelled NEET UG 2026 examination over paper leak allegations. Authorities are now investigating allegations that a so-called "guess paper" was circulated amongst students well before the examination. Roughly 120 of the 410 questions allegedly appeared in the Chemistry section of the real examination. The guess paper was reportedly also sent to students via WhatsApp.