"This manga and that anime are the same story."
話 - はなし is a story or a conversation. The verbs "to talk" or "to chat" can be written as 話す/話します [はなす/はなします] or 話(を)する/話(を)します [はなし(を)する/はなし(を)します].
They are NOT the same story. The manga was so much better. I can't even believe the changes they made with the anime. The protagonist's design is totally different and this character got completely left out!
Because onaji is an adjective describing the noun hanashi. That answer is too full of grammar points to really feel like a good explanation, but that's the best i can do. Sorry about that
If 同じ is a na-adjective, then why is it not followed by な if it is attributive to 話?
Is it a na-adjective? From what I gathered, the use of "the same" is just a description that ties two ideas or objects together, rather than describing them. It can work like an adjective but it's not exactly the same as either group.
So since then, I gathered that 同じ is what is known as "adverbial nouns." Adverbial nouns are scarce but behave on a case-by-case basis and are thus best to be memorized in usage. You may know other adverbial nouns like とても, たくさん, and もし.