1. Do you consider the Task or Mission cards as a kind of item?

Whenever discarding your items due to getting insane or unconscious, do you count the Task or Mission cards as items?

The appropriate information has been not found at all.

In my opinion, although the cards are drawn and bought in a common and unique deck,

they are no longer items once being taken by any investigators.

2. What does "for every dice of 1 or 2" means?

If I roll two dice, which cause the result 1 and 2, is that double success or single one?

Whenever I play Arkham Horror, I found many questions, can I master Arkham someday?

From the Dunwich Horror rulebook, pag. 5: "Tasks are a type of item found in the Common Item deck, while Missions are items found in the Unique
Item deck". I've always considered them as normal items, even because you can give another investigator a task or a mission. So in my opinion they do count as items even when you go unconscious / are driven insane.

As far as your second question is concerned, I'm afraid I didn't get the point. Could you kindly contextualize the sentence you're referring to?

Tasks and Missions are still Common and Unique items, respectively. I'm sure it's in the rules, so you probably just missed it.

But I don't know what your second question is referring to.

To answer your first question: yes, Tasks and Missions are considered items.

I don't know what you mean by the second question though. Rolls of 1 or 2 are not successes at all, only 5s and 6s.

Trish's Boyfriend said:

www.arkhamhorrorwiki.com/Good_Work_Undone

If the two dice showed '1' and '2' respectively, you'd have to put two clue markers on the card.