Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

Known by all without exception, Forever here, for your protection, Sometimes strong, sometimes weak, Right after the night I come - hot and chic. And while millions of miles away, I always get to you, I find my way. No life around could do without me, Can you guess what I might be?

When I go in I might cause pain. I cause you to spit and ask you not to swallow. I can fill your hole. What am I?

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

What does the following BrainBat signifies?

ABCDEFGHIJKLMNOPQRSTUVWYZ

QQQQQQQQQQQQQQQQQQQQQQQQQ.

Can you solve this picture maths equation?

O_er_t_o_

Complete the missing letters of the given word.

I am dry when I go inside, but wet when I am pulled outside.
The longer I am inside, the stronger I get
When I am completely out, I am wet and I literally sag
Who am I?

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.

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?