Which word does the below Plexor means ?

There is a family that live in a round house. The two parents go out for a movie and leave a babysitter to watch their son. They come back and the kid was not there. Some one kidnapped him. The maid said she was cleaning in a corner. The cook said he was making pizza. The babysitter said she was getting a board game. Who kidnapped him.

What does the following represent?

N N N N N N N

A A A A A A A

C C C C C C C

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

What building has the most stories?

In one of the popular batman series movie "Batman Forever", there was a riddle that goes like "Tear me off and then scratch my head and I was red then and now I am back. Who am I?

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

What's the only room from which no one can enter or leave

13 decks of cards have been mixed. What is the minimum number of cards that must be taken out from the above-mixed cards to guarantee at least one 'four of a kind?

No matter how little or how much you use me, you change me every month. What am I?