Muslims,where in quran or in hadith it says that halal slaughter must be done by cutting the neck?

Mohammed was the last prophet and his teachings are the only ones Muslims are to follow till the end of time. Slaughtering and letting it bleed to death (takes two or minutes) is cruel and barbaric but unfortunately your religion doesn't allow change and progress. It operates on the arrogant assumption that the teachings of Allah/the prophet are perfect and don't need to be changed.