The Infallibility Of The Qur'An
The Qur’an is revealed in a historical perspective. Like any other books, the information of the background is required to understand in what context the Qur’an talks. This information comes from established history. For example, when the Qur’an mentions the battle of badr or the treaty of Hudaybiya we need to know about these events. Hadith on the other hand is individual reporting, in which the proohet occasionally interpreted a verse or two of the Qur’an. He didn’t interprete the whole Qur’an. This interpretation was arbitrary, not necessary, otherwise he must have interpreted the whole Qur’an on his own and should have not waited till someone asked for an explanation. Hadith is very helpful in understanding the Qur’an but it is not its prerequisite. Answer to your second question is, one can appreciate the coherence of the Qur’an by reading its translation. You can read the translation of Ghamidi saheb which is particularly indicates the conherence of the Qur’an. His translation is available both in book form and online.