a)Can White prevent Black from capture the pawn?
b)Can Black stop the advanced of the White pawn?
a)Yes.White can prevent black from capture the pawn by 1.Kf5 Ke3 2.Ke5 Kd3 3.Kd5 Kc3 4.Kc5 Kb2 5.a4
b)Black cannnot stop the advanced of the white pawn.
One thing to remember that if white miss the move 1.Kf5 then the continuation of this game lead to a draw.
Thanks to Cikgu for solving this problem.