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 four steps you need to move the word 'cold' From 'warm' by replacing one alphabet at a time such that every word formed at each step is acceptable in English Dictionary.

John enters a small room. The Door Closes.
When the door opens, John is in a larger room.

Explain?

A boy was at a carnival and went to a booth where a man said to the boy, "If I write your exact weight on this piece of paper then you have to give me $50, but if I cannot, I will pay you $50." The boy looked around and saw no scale so he agrees, thinking no matter what the carny writes he'll just say he weighs more or less. In the end the boy ended up paying the man $50. How did the man win the bet?

When I get multiplied by any number, the sum of the figures in the product is always me. What am I?

It's a protector.
It sits on a bridge.
One individual can see directly through it, while others wonder what it hides.

What is it?

What word begins and ends with an E, but has only one letter?

You see me once in June, twice in November, and not at all in May. What am I?

I don't get anymore wetter, no matter how much rain falls on me.

The more of this there is, the less you see. What is it?