What work can one never finish?

The below given figure comprises of a pattern through which you can determine the missing letter. Can you push your mind to find the pattern and add the missing letter?

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

An American nightclub called 'The Coconut Grove' had a terrible fire in which over 400 people died. A simple design flaw in the building led to a high death toll. Subsequently, regulations were changed to ensure that all public buildings throughout the country eliminated this one detail, which proved deadly. What was it?

I am the beginning of everything, the end of everywhere. I'm the beginning of eternity, the end of time and space. What am I?

I can write cow in 13 letters.

Can You?

Below rebus represent famous DiCaprio movie. Can you name it?

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

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

In a town, there are four houses located at different distances from each other. Following are the distances:

The third house is 60 meters apart from the first house.
The fourth house is 40 meters apart from the second house.
The third house is 10 meters nearer to the fourth house than it is to the second house.

Can you find out the distance between the fourth and the first house?