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

What do you think with the below Picture ?

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

You’re out on the water and see a boat filled with people. You look away for a second and look back again, but this time you don’t see a single person on the boat. Why? Hint: The boat did not sink.

What is the fastest way to double your money?

What are the next two letters in the following series and why?
W A T N T L I T F S _ _

*Hint: Check Puzzle Title

Why are all black people so quick ?

What goes up but never comes down?

In a science lab, a petri dish hosts a healthy colony of yeast for an experiment. Now every minute, all the yeast cells divide into two. At noon, there was just a single cell of yeast and at 1:22, the Petri dish was half full. Can you calculate when the dish will be full of yeast?

I look at you, you look at me I raise my right, you raise your left. What am I?