Shortest Distance Between Two lines

The shortest distance between the two lines $L_1: x=k_1; y=k_2 \& L_2: x=k_3; y=k_4$ is equal to

The shortest distance from $\left(1,1,1\right)$ to the line of intersection of the pair of planes $xy+yz+zx+y^2=0$ is

The shortest distance between any two opposite edges of the tetrahedron formed by planes $x+y=0, y+z=0, z+x=0, x+y+z=a, a>0$ is a constant and is equal to

Find the magnitude of the shortest distance between the lines $\frac{x}{2}=\frac{y}{-3}=\frac{z}{1}$ and $\frac{x-2}{3}=\frac{y-1}{-5}=\frac{z+2}{2}$.