How is a fly different from a mosquito?

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 a word that begins with the letter “i.” If you add the letter “a” to me, I become a new word with a different meaning, but that sounds exactly the same. What word am I?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

If you paint a brown house white it will become a white house. If the stoplight changes from red to green, then the light is green. So, if you throw a white shirt into the Red Sea, what will it become?

When is the top of a mountain similar to a savings account?

If,
29 - 1 = 30
9 - 1 = 10
14 - 1 = 15

Based on similar logic, Can you prove that the below algebraic equation is true?
11 - 1 = 10 ?

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

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

In a particular village, only two barbershops exist.

The first shop has a handsome barber with a neat haircut who is handsomely dressed in clean clothes and is extremely humble with his body language. The place is clean and looks hygienic.

In the second shop, you can find a barber with shabby clothing. His hairs are weirdly cut and his clothes still have the stains from last night's dinner. The place is not clean as well and reeks a bit.

You visit the village for the first time and decide to get your haircut. Which barbershop will you like to go for that and why?