#1: Consider the reaction:
At equilibrium, there is no net change in concentrations of either reactants or products and occurs when both forward and backward reaction rates are equal to one another.
The term dynamic refers to the fact that even though there is no net change in reactants or products, it doesn't necessarily mean that the forward and backward reactions have stopped. They do still occur, just at equal rates.
#2: You're given the reactants and products. It's just a matter of writing it out and balancing the numbers out if need be:
Assume that the reaction is strictly forward and calculate the yield of chloromethane. Whatever yield you get, there is no way that your reaction in equlibrium will produce more chloromethane than that produced from a strictly forward reaction.
For b), I don't know what you mean by "percentage reaction of equilibrium" but to find out which reaction is favoured, consider the equilibrium constant:
If , then the forward reaction is favoured (makes sense, the numerator is larger than the denominator meaning the ratio is bigger than 1).