What does this rebus riddle means ?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

why number 8549176320 is one of a kind?

We are a group of eight brothers. We consider the weak, yet we protect the king in every battle. If we move ahead, we never turn back. Who are we?

I have eight fingers and two thumbs but I do not live. What Am I?

Once while in his court, King Akbar asked Birbal to write something on a wall that makes one sad when read in good times and makes one happy when read in sad times.

He took only a few moment and wrote something that fit the requirements. What did he write?

What word begins and ends with an E, but has only one letter?

The following alphametic has only one solution. Can you find it?
ENLIST + SILENT + LISTEN = ANAGRAM

PS: You may start the number from 0.