Depending on what you mean by inception, maybe yes, maybe no. It was not initially written down exactly as we have it today, no. It was eventually canonized into its current form, yes, if that's what you mean, though exactly when and by whom is unclear.
Kinda. There were several variants in the early days, until one version was declared the true and only correct version; every Koran since then has been a copy of that one.
Depends on how you define inception. Muhammad himself was illiterate so the job of writing down came to his followers. Many of them wrote on parchments which were kept in random order. Over years people added more parchments to the pile. Soon there were several hundred versions of koran. I think Muhammad's third generate Khalif managed to create one "authentic" koran and burned all other versions.
Yes. Its preservation is promised by Allah. In practice, I think one reason for that has been that it's encouraged to memorize it (from its inception), the original blockchain :)
[EDIT] https://en.wikipedia.org/wiki/History_of_the_Quran