Salam curious cat. This allegation of tampering/burning keeps coming up. The allegation arises out of ignorance of Arabic. The question belies a colossal misunderstanding of Arabic words. The term Quran means that which spoken by Allah. Qara'a/Iqra/Quran. It is not possible to tamper with what comes out of my mouth, how can anyone tamper with what comes out of Allah? How is it possible to tamper with that, that a man cannot touch or exert control over? Please examine your question. Rephrasing your question, you are asking how do you know the words that issued out of Allah have not been tampered with. The very concept is erroneous. Allah protects his word. Allah is mighty wise.