1)
"Kol Demei Achicha". Why did Hashem refer to the blood of Hevel in the plural?
1.
Rashi #1 and Targum Onkelos: Because He was referring also to the blood of all Hevel's potential offspring, whom Kayin prevented from coming into the world 1 with his murder.
2.
Rashi #2: Because of the many wounds that he inflicted on his body, not knowing on which limb to strike him and kill him. 2
2)
Why does it say that the blood is crying "from the ground"?