What does below chemistry rebus means?

My cousin lives in one story house in Antarctica. His house is made the of-of sandstone. what is the color of stairs?

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

John was running from 40 thieves. John has got 3 gold boxes which weigh as 4kg, 2kg, and 1kg respectively. A witty man asked John to stay with him for seven days in exchange for 1kg gold per day. John needs to stay there for seven days and also do not want to give the witty man any advance. How can John pay for his seven days stay?

You Throw The Outside, Cook The Inside
Eat The Outside, Throw The Inside.

What Is It?

There are are five things wrong with this sentence; only geniuses will be able to to spot all of the mitstakes

The dirtier I get, the whiter I look. Who am I?

Double it and multiply it by 4. Then divide it by 8 and you’ll have it once more. What number is it?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

0 0 0 = 6
1 1 1 = 6
2 2 2 = 6
3 3 3 = 6
4 4 4 = 6
5 5 5 = 6
6 6 6 = 6
7 7 7 = 6
8 8 8 = 6
9 9 9 = 6

You can use any mathematical symbols in the space provided to make all above algebraic expressions true.