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

Prove that the below maths equation is true.

8 + 8 = 91

It belongs to you, but other people use it more than you do. What is it?

A beggar on the street can make one cigarette out of every 6 cigarette butts he finds. After one whole day of searching and checking public ashtrays the beggar finds a total of 72 cigarette butts. How many cigarettes can he make and smoke from the butts he found?

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.

What is full of holes but still holds water?

What does the following BrainBat signifies?

ABCDEFGHIJKLMNOPQRSTUVWYZ

QQQQQQQQQQQQQQQQQQQQQQQQQ.

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

I have branches, but no fruit, trunk or leaves. What am I?

What does the below rebus riddle means?