Can you replace the question mark with the correct number in the below table sequence?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

The first person saw the bridge step on it and crossed,
the second person saw the bridge did not step on it but crossed,
the third person did not see the bridge did not step on it but crossed.
Who are these people?

In a town, there are over 100 flats.
Flat-1 is named first flat.
Flat-2 is named second flat.
Flat-3 is named third flat.

A visitors 'Victor' decides to walk through all the flats, he finds all the flats except flat-62.
Victor later founds that the local of the town have given it another name.

What is the name of the Flat?

Can you place three balls such that the equation shown in the picture holds true?

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?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

I am lying and I always lie. Tell me whether I am lying or telling the truth.

Can you identify the famous TV character from the rebus below?

Name a key which is hardest to turn.