It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Sherlock breaks into a crime scene. The victim is the owner who is slumped dead on a chair and have a bullet hole in his head. A gun lies on the floor and a cassette recorder is found on the table. On pressing the play button, Sherlock hears the message 'I have committed sins in my life and now I offer my soul to the great Lord' and followed a gunshot Sherlock smiles and informed the police that's its a murder.

Why did he think so?

Solve the equation in the image by looking at the pattern closely.

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

What is the word or phrase?

Solve the following series:
AZ, GT, MN, __, YB

What breaks yet never falls, and what falls yet never breaks?

Paul's height is six feet, he's an assistant at a butcher's shop and wears size 9 shoes. What does he weigh?

I have lakes with no water, mountains with no stone and cities with no buildings. What am I?

There is a shop where written:
Buy 1 for $1
10 for $2
100 for $3
I needed 999 and still only paid $3. How could this be financially viable for the shop-keeper?