Which of these factors does not govern the stability of a conformation in acyclic compounds?

Which of the following describes the best relationship between the methyl groups in the chair conformation of the substance shown below?

What,if anything,can be said about the magnitude of the equilibrium constant $K$ for the following equilibrium?

Which statement is true for cyclohexane?

One of the configurations of $n$-butane is shown in the given figure. An anticlockwise rotation of $C_2$ around the $C_2-C_3$ bond by $120^\circ$ will lead to:

Statement $I$: Staggered conformation of ethane is more stable than the eclipsed conformation.
Statement $II$: The torsional strain in staggered conformation is more than in the eclipsed conformation.