Not 1.Kb1 Sxd2+ 2.Ka1 Kb3 - the position is dead after 1...Sxd2
But 1.Kb1 Kb3 2.Ka1 Sxd2=

Not 1.d1Q Sd2 2.Qb3+ Kxb3 as after 2.Qd3+ White must capture bQ with K or S, leading to stalemate or draw, so that position is dead;
But 1.d1B Sd2 2.Bb3 Kxb3

Finally 1.d1R Kb3 2.Rd2 Sxd2