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.

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'

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

John can place six large boxes or nine small boxes into a carton.

Can you find out in how many cartons can he place sixty-six boxes in total?

Two batsman each on 94 runs. Seven runs needed to win in last 3 balls. Both make 100*. How?

There is one thing that goes round the house and also inside the house but never even share a brief touch. What is it?

John was piloting a plane behind a car but was never able to overtake it. Why?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

Fate has decided that you will only be pleased to meet me when you need me

Maybe that is why, when I am working, I start working

However annoying I may be to the regulars, the little ones are always inspired

I will always be waiting if you try to reach me

How many of you can guess my name, let me see

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?