Can you find the missing piece of the Porsche?

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

What Word am I Looking For ?

Rahul decided to meet Simran so he boards a local train from Bombay station. Just after the station, there is a 1km long tunnel. The train starts and is now accelerating. Rahul is a claustrophobic guy, so what is the best position for him to sit?

Can you start the fire using two pieces of wood?

Railroad Crossing, look out for the cars. Can you spell that, without any R's ?

Using eight eights and addition only, can you make 1000?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

There are three identical triplets sisters. Demi is the oldest of them all and she always speaks the truth. Diana is the next one who is a liar always. Drew, the youngest of them all speaks both truth and lies randomly.

On a rainy day, a family friend Victor visited them. Since there were starkly identical, he was not able to recognize them. Thus to clarify, he asked one question to each one of them.

He started with the one standing on the left and asked, 'Which sister is in the middle of you three?' She answered, 'That's Demi.'

Then, he asked the one standing in the middle, 'What is your name?' She answered, 'I am Drew.'

Finally, he asked the one standing on the right, 'Who is standing in the middle?' She answered, 'She is Diana.'

Victor was left baffled. He asked the questions three times and received different answers every time.

Can you tell who was who?

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

I have an eye but still cannot see.

Who am I?