What does this Rebus Picture means ?

Before Mount Everest was discovered, what was the highest mountain in the world?

I taste better than I can smell. Who am I?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

When Jack was six years old he hammered a nail into his favourite tree to mark his height. Ten years later at age sixteen, Jack returned to see how much higher the nail was. If the tree grew by five centimetres each year, how much higher would the nail be?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

Two in a corner, one in a room, zero in a house, but one in a shelter. What is it?

What part of Turkey has the most feathers?

As easy as you can get into me, it is as hard to get out of me.

Do you know what I am?

A man dies of old age on his 25 birthday. How is this possible?