What building has the most stories?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

It is a six-letter word.
The first four letters are me.
The second and last letters are the same.
The fourth second and last letter is payment.

Who is it?

A man lives on the fifteenth floor of an apartment building. Every morning he takes the elevator down to the lobby and leaves the building. In the evening, he gets into the elevator, and, if there is someone else in the elevator, or if it was raining that day, he goes back to his floor directly. Otherwise, he goes to the tenth floor and walks up five flights of stairs to his apartment. Can you explain why he does this?

There is a box full of marbles,
all but two are blue,
all but two are green,
and all but two are red.

How many marbles are in the box?

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

Can you find the 09 errors in the picture below?

Solve this riddle by finding the odd one out from the rest.

What has 13 hearts but no other organs?