Which conformation of cyclohexane is chiral?

Which one of the following conformations of cyclohexane is chiral?

Give the difference between eclipsed ethane and staggered ethane.

The structures shown below represent .......

Isomerism due to rotation around the $C-C$ single bond is known as:

On another planet,the gauche and anti forms of $1, 2-$dichloroethane freeze and single bond rotation stops. Under these conditions,these two forms can be considered as: