What brings you down but never up?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

why number 8549176320 is one of a kind?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

What work can one never finish?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?

John was running from 40 thieves. John has got 3 gold boxes which weigh as 4kg, 2kg, and 1kg respectively. A witty man asked John to stay with him for seven days in exchange for 1kg gold per day. John needs to stay there for seven days and also do not want to give the witty man any advance. How can John pay for his seven days stay?

Solve the following series:
AZ, GT, MN, __, YB

If EELS + MARK + BEST + WARY = EASY

What does HELP + BARK + WARD + LEAD equal?