Work done in moving a positive charge on an equipotential surface is

Which of the following figures shows the correct equipotential surfaces of a system of two positive charges?

Find the equation of the equipotential surface for an infinite cylinder of radius $r_0$,carrying a charge of linear density $\lambda$.

$A$ charge of $20 \, \mu C$ is placed at the origin. What is the potential difference between the points $(5a, 0)$ and $(-3a, 4a)$?

The nature of the equipotential surface for a point charge is:

$A$ metallic sphere has a charge of $10\,\mu C$. $A$ unit negative charge is brought from $A$ to $B$,both $100\,cm$ away from the sphere,with $A$ being east of it and $B$ being west of it. The net work done is........$joule$.