Accuracy of suttas

The suttas were as far as I heard transmitted orally, and it was only several hundred years later that the teachings were put on to paper. Now my questions: i) Do you believe in every sutta? For example: That a person suddenly attained sottapanna or arahantship? Notice: It doesn't matter whether it happened or not because it has not real implications on me, but it's as always this easy and unrealistic kind of thinking that people often employ ii) Couldn't it be the case that there are also many 'later alterations' to fit the dhamma to one's own/to culture's liking? iii) Connected to question i): How do you interpret devas? And how do you verify 'post-morten' rebirth? Isn't it in contradiction of anatta? Didn't the Buddha teach that the Dhamma can be experienced in the here and now? Why do the 4NT (and N8P) not mention rebirth? iv) Most people do not translate suttas by their own. They take the words from scholars and monks, which often copy from each other. Is this the critical thinking that Buddhists often speak of?