What is the end of everything?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Suppose you are sitting in an interview and the interviewee asks you an aptitude question.

You have three buckets with a capacity of 4 litres, 8 litres and 10 litres and you have a large tank of water. Now you have to measure 3 litres of water precisely using those buckets. How will you do it?

Two guards were guarding the camp.Guard-1 was looking towards the south to make sure no threat is coming from the road.Guard-2 was looking at the north to make sure no threat is coming from the top. Suddenly Guard-1 ask the Guard-2 why he is smiling?How Guard-1 knows that Guard-2 is smiling?

What Time Should the last watch show in the below figure?

All of Jacob's shoes are red except two.
All of Jacob's shoes are green except two.
All of Jacob's shoes are yellow except two.

How many shoes does Jacob have?

Through your logical capabilities, can you make 7 an even?

Look at the picture and find out which square is not linked with any of the other squares.