Quickly Solve this riddle

7 - 4 + 3 * 0 + 1 = ?

A Detective reviewed the information they had on the case so far.

A lady named 'Caterina' was found shot and they already had a list of suspects - Ankit, Tarun, Harish, Manoj and Manish.
The killer is a fan of challenges him by leaving notes ad various places.
* The first was found in a toilet room.
* The second was found in an art room.
* The third was in a restroom.
* the fourth in an underwater room.
* The fifth at the no-smoking room.

All of the notes read the same thing, 'The clues are where you find the notes.' Yet, nothing was found at any place the notes were.
Detective the genius, immediately solved the case.
Who was the killer?

Forwards I am heavy, backward I am not. What am I?

Keyboard words are not in alphabetical order, Why?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

The measurement of time, That can't be found on a clock, But can be looked upon on a map.

Who is He ?

What has 13 hearts but no other organs?

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

What Word am I Looking For ?

You find yourself in a strange place guarded by two guards.One of the guard always say truth while other always lies.You don't know the identity of the two.You can ask only one question to go out from there. What should you ask?

Why is the Hole below a Lock?