Skew lines

Equation of the line of the shortest distance between the lines $\dfrac x1=\dfrac y{-1}=\dfrac z1$ and $\dfrac{x-1}0=\dfrac{y+1}{-2}=\dfrac z1$ is :

Two lines $L_1:x=5,\ \dfrac y{3-\alpha}=\dfrac z{-2}$ and $L_2:x=\alpha,\ \dfrac y{-1}=\dfrac z{2-\alpha}$ are coplanar. Then $\alpha$ can take value(s)

If the straight lines $\dfrac{x-1}2=\dfrac{y+1}k=\dfrac z2$ and $\dfrac{x+1}5=\dfrac{y+1}2=\dfrac zk$ are coplanar, then the plane(s) containing these two lines is(are)

The shortest distance between $L_1$ and $L_2$ is