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

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?

A thief enters a store and threatens the clerk, forcing her to open the safe. The clerk says, “The code for the safe is different every day, and if you hurt me you’ll never get the code.” But the thief manages to guess the code on his own. How did he do it?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

Which wheel of car does not rotate when you turn your car right?

What does this rebus puzzle means ?

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

What goes through cities and fields, but never moves?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

Take 9 from 6, 10 from 9, 50 from 40, and leave 6.

How Come ??