The traditional (Islamic) history of the Qu'ran. During the time of the Prophet Mohammed, people would memorize the QUran as it became revealed (it was first an oral document not a written one) and some of the literate people around Mohammed would write them down on whatever writing material had been avialible, but Arabic did not have a formalized written component at that time so everythingis written in different dialects of Penisular Arabia, seven different dialects is the traditional number representating seven different regions of Arabia at the time.

After Mohammed's Death, there were still thousands of people who memorized the Quran but there was an effort by the third caliph Uthman to get a standardized written version. So he ordered the collection of all Quranic fragments to studied and choose to have the written Quran be exclusively of the Hedjazi dialect (Hedjaz is the region were Mecca and Medina are) and ordered the rest to be burned (one of the "lawful ways to dispose of the Quran).

Recently there was a Manuscript found in Sanaa, Yemen that was a 7th century Quran that had been written over an even earlier version of the Quran. As far as had been released to the public the two Quranic texts found on the manuscripts are largely the same with some differences. This find seems to support the claim that there was a period of standardization in the decades after Mohammed, but possibly slower spread then the traditional narrative implies.

In addition to this written documentation there are the people that memorized the Quran orally as i meantioned before. These people were and are given the title Hafiz by Muslims and is still greatly valued in Muslim societies. Unlike the written version, there wasn't a period of standardization in the oral version. Nowadays there are 7 oral versions of the Quran representing the regional dialects of the time of revelation that are recognized as canonical and each tradition traces is lineage back to a Mohammed's time. They don't differ in substance.

So there is the oral history of the Quran that remained standardized till today, and the written history of the Quran has standardized after Mohammed's death. this is the traditional narrative.

Now for the language aspect. the Arabic in the Quran is a snapshot of 7th century Hedjazi Arabic. And since its standardization has remained the same. but Modern Arabic is not Quranic Arabic. Its readable to Modern readers but kinda like how Modern English (Shakespeare) vs Middle English (Canterbury Tales). The structure is there but its not exactly the same and its difficult to read going in blind about the differences. This is actually a fairly relatvate Issue in muslim communities aroudn the world because sometimes rote memorization of the Quranic Arabic is the only thing taught, and not the meaning of the words and Many Muslims will never read the Quran in a way they can understand (either modern Arabic or one of the thousands of other languages Muslims speak) and they rely on interpreters to explain the meaning. For example one of the listed certifications for being a alim (a scholar of Islam) in many places, is being fluent in Quranic Arabic, not Modern Arabic.