Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see? What is it?

It's a 7-letter word.
If we remove 1 letter from it, it remains the same.
If we remove 2 letters from it, it remains the same.
If we remove 3 letters from it, it remains the same.
If we remove all the letters from it, still it remains the same.
What is it?

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

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

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

Find the hidden panda in the image below.

A man was driving a black truck. His lights were not on. The moon was not out. A lady was crossing the street. How did the man see her?

With the help clues provided in the image, can you find the 5 digit key?