What has many keys but can’t open a single lock?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

Fate has decided that you will only be pleased to meet me when you need me

Maybe that is why, when I am working, I start working

However annoying I may be to the regulars, the little ones are always inspired

I will always be waiting if you try to reach me

How many of you can guess my name, let me see

What breaks yet never falls, and what falls yet never breaks?

If nine thousand, nine hundred nine dollars is written as $9,909,
how should twelve thousand, twelve hundred twelve dollars be written?

If you were to put a coin into an empty bottle and then insert a cork into the neck, how could you remove the coin without taking out the cork or breaking the bottle?

John asked Jack, "The time right now is 7 pm. Can you tell me what will be the time 23, 999, 995 hours later ?"

While Bella does not know the answer, do you ?

Prove that twice of ten is the same as twice of eleven.

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

I hide my treasure in the ground, my tail is big and fluffy. If you spot me in a tree, please don’t call me scruffy. What am I?