What has 13 hearts but no other organs?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

I had an infinite supply of water and 5 litres and 3 litres jars.

How would you measure exactly 4 litres in the least number of steps?

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

I am the one who remains awake when you sleep. But I need to rest when you awake. Who Am I?

Why 1729 is a magic number? Answer Logically.

What is red and smells like blue paint?

John left on a horse on Thursday , was gone for two days, and came back on Thursday after completing his work. How did that happen?

There are 3 apples in the basket and you take away 2. How many apples do you have now?

Using mathematical symbols like +, -, and x in order to make the equations correct. Replace # with the above-given symbols.

9 # 8 # 7 # 6 # 5 # 4 = 91