[asharbiq]

They are neither Ahlul-Kitab nor Ahlul-Watermelon, they are either Deviant Muslims or Kouffar based on their beliefs, not all Twelvers share the same beliefs.

Regarding the Quran many of the companions had their own written copies and many had written notes and tafseers, the problem with the Shia is that they have narrations that state that there is a completely different Quran and if I recall the term "It has no letter from the Quran you have in your hands" was used.

As for the Twelvers, according to them 'Ali (ra) is some sort of demi-God who knows everything whereas the Islamic view of the scholars state that he was one of the biggest companions and the probably the most knowledgeable during his Caliphate but he was not infallible nor did he know everything.

قلت: يا رسول الله، إنا نزل بنا أمر ليس فيه بيان أمر ونهي، فما تأمرنا، قال: شاوروا الفقهاء والعابدين، ولا تمضوا فيه خاصة 'Ali (ra) asks the Prophet SAWS: "O messenger of Allah, if we encounter a situation and there is no clear divine text to prove its ruling if it's permissible or not, what do you order us to do then?" He SAWS said: "Consult the pious worshippers and the knowledgeable in matters of religion, do not take a decision on your own."

sources: Tareekh Khalifat ibn Khayyat p66, Manhaj 'Ali ibn abi Talib fil Da'awa ila Allah p78, Seerat Ameer al-Mumineen 'Ali by al-Sallaby p68.

And there is the famous incident in which 'Ali (ra) burns some heretics who were raising him above his level then ibn 'Abbas (ra) criticizes him for doing so as the Prophet SAWS forbade the punishment by the fire.

As for the Quran 'Ali ibn abi talib (ra) was extremely knowledgeable in Tafseer and Asbab al-Nuzoul and he would ask the people to come to him and learn about the explanation of verses as he says in the famous Hadith: "Ask me, Ask me, Ask me about the book of Allah"