What does this Rebus Picture mean?

I have a hole in my back and legs I lack.
I live where I can’t breathe and I eat without teeth.
What am I?

By including only four matchsticks in below picture, you have to make "Four Triangles And Two Squares"

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

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

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?

In the attached figure, you can see a chessboard and two rooks placed on the chess board. What you have to find is the number of squares that do not contain the rooks. How many are there?

Make the seating arrangement of 10 children in such a way that there are 5 rows with 4 children in each row.

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

What is more useful when it is broken?