What has 13 hearts but no other organs?

Can you replace the question mark with the correct number?

Which statement is true out of the following?
One statement here is false.
Two statements here are false.
Three statements here are false.

You are given a cube that is made with the help of 10x10x10 smaller cubes summing up to a total of 1000 smaller cubes. You are asked to take off one layer of the cubes.
How many remain now?

On 26-01-2022, Juli was murdered at her house in a city in India in the afternoon. There were three suspects in the murder and the following are the statements that were given by them:

John: I visited my village that day.
Jacob: I was out to deposit my house tax in the municipality office at that time.
Jonny: I was at a friend's place having lunch at that time.

Can you find out who is the murderer?

Take one out and scratch my head, I am now black but once was red. What am I?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

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?

John was piloting a plane behind a car but was never able to overtake it. Why?