I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

In the picture given below, can you find out which digit will take place of the question mark?

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

What Word am I Looking For ?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

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

What is red and smells like blue paint?

Can you count the number of triangles in the picture below?

What month of the year has 28 days?

What do you think with the below Picture ?

There was a kingdom in which the king had no heir to take over his thrown. Even the queen was dead and he himself was on the verge of dying. He thought about it and then summoned all of the teenagers. He gave one seed each to all of them and asked them to grow the plant. He announced that the one with the most beautiful plant will become the king/queen of the empire after the death of the king.

After a month, all of them were called. The king looked at all of the plants but announced the girl with an empty pot as the queen of the empire. Why?