You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

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.

Give it food and it will live; give it water and it will die.

You throw me out when you want to use me and you take me in when you don't want to use me.

Who Am I?

The Puzzle: A girl, a boy, and a dog start walking down a road.

They start at the same time, from the same point, in the same direction.

The boy walks at 5 km/h, the girl at 6 km/h.

The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.
How far does the dog travel in 1 hour?

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

What demands an answer, but asks no questions

I have no life, but I can die. What am I?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

The more you take me, the more you leave me behind.
Who Am I?