Eight of us go fourth, not back, to protect our king from an attack. What are we?

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.

A person was killed at a house party. When the police arrive, there are six people present in the house who are the friends of the victim. The name of the friends is Rohit, Aman, Nick, Gagan, and Randy.

Near the dead body, they find a few numbers written with blood by the victim on the floor. The numbers are 8, 5, 4, and 11.

The police arrests one of the friends for the murder. Whom did they arrest and why?

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

If you remove one from eleven, it becomes ten. If you remove one from nine, it becomes ten.

How is this possible?

Why did the Girl throw the butter out of the window?

What animal walks on four legs in the morning, two legs during the day, and three legs in the evening?

Oedipus, the king of Thebes, figured out the answer to the riddle:

When it is alive we sing, when it is dead we clap our hands. What is it?

I know a country, If you remove the last alphabet of its name, it will become a part of your body. Do you name it?

I know a nine-letter word having only one vowel.
Do you ?