What is full of holes but still holds water?

What does below chemistry rebus means?

Can you find out the remainder when 3^300 is divided by 5?

What is the fastest way to double your money?

I have Rs.50 and I spend it in the way as below.

A man escapes from jail using help from his girlfriend. The investigators suspect four girls of being the man's girlfriend.

Out of those four girls, one is his girlfriend who is lying. Two of the girls are completely innocent and are speaking the truth. One of the girls is the man's sister who is helping the girlfriend lie. Following are the statements from all four of them:

Ariana: "Myrna is his girlfriend."
Jane: "Angelina is lying."
Angelina: "Ariana is lying."
Myrna: "Jane is not his sister."

Can you find out who is the man's sister among them?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

Why is 6 afraid of 7?

I am the beginning of everything, the end of everywhere. I'm the beginning of eternity, the end of time and space. What am I?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?