Well if the rock doesn't move, then there is no amount of work done. There is no work done on an object if a force is applied to the object but it DOES NOT change its position, in this case is the rock.
Explanation:
Given:
Solving for
:

where:

Integrating to get
with initial conditions
:

Integrating to get x with initial conditions x(0) = 0:

When t=T:


Yes because if they are further away it makes it hard for them to attract each other
They all move through empty space at the speed of light
Answer:
It will do nothing. The forces are balanced and the ball's motion will not change