why number 8549176320 is one of a kind?

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Complete the missing letters of the given word.

I have one of the three numbers: 1, 2, or 3 in my mind. I speak only truth. You can ask me just one question for which I will only reply in yes or no or don't know. What question will you ask from me so that you are able to know the number?

Out of the nine cats that you can see in the picture, there are only two that are completely identical. Can you find them out?

A man calls his dog from the opposite side of a river. The dog crosses the river without a bridge or a boat and manages to not get wet. How is this possible?

What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

John is found dead in his office at his desk. The police have narrowed the suspects down to three people: Mrs. Jacob, John’s wife Hena and his business partner Jason . All three visited John on the day of his murder, but all three provide the police with stories of explanation as to the reason for their visit.
Police found John with his wrist watch still on his right arm, a torn up picture of his wife laying on the floor beside the trash can, and an ink pen in his right hand. On the desk, the police found a name plate, a telephone that was off the hook, and a personal calendar turned to the July 5th page with 7B91011 written on it. After examining this evidence, the police knew their suspect. Who was it ?

Replace the question mark with the correct number below.

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?