What work can one never finish?

There are three Athletes (John, Tarun and Harish) and their individual Coaches (Jacob, Meenaxi and Priyanka) standing on the shore.
No Coach trusts their Athlete to be near any other Coach unless they are also with them.
There is a boat that can hold a maximum of two persons.
How can the six people get across the river?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

In the given figure, move three matchsticks so that the resulting figure contains two rectangles.

What is so fragile that saying its name breaks it?

I know a country, If you remove the last alphabet of its name, it will become a part of your body. Do you name it?

Can you name an animal whose killing cannot be performed without spilling your own blood?

I have teeth but i don't bite. Who Am I ?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

Using eight eights and addition only, can you make 1000?