On a special event at the prison, 5 prisoners John, Jacob, Krist, Tang, and Dang given a chance to go to a sauna and can bring one thing with them.

Following are the things that the prisoners bring with them.
John: A soda
Jacob: Thermos
Krist: Book named "How to kill"
Tang: A Walkman
Dang: Harmonica

Since it is a Sauna, no one can see each other. After a while When the steam is switched, Tang was found dead and there was blood all around.
J Bond was called and he instantly come to know who can be the murderer. How?

Can you count the number of seconds in a year?

Clue: You need to bother about calculation.

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

There is something which is always coming but never arrives?

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

Our product and our sum always give the same answer. Who are we?

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

A worker is to perform work for you for seven straight days. In return for his work, you will pay him 1/7th of a bar of gold per day. The worker requires a daily payment of 1/7th of the bar of gold. What and where are the fewest number of cuts to the bar of gold that will allow you to pay him 1/7th each day?

Can you arrange four 9's and use at most 2 math symbols, to make the total 100?