Please help me, I have a question about the Bible?

No God did not change His mind. Back in Genesis when we are the fruit we gave our power and authority that God had given us to satan because we obeyed him instead of God. It caused a separation between us so to speak. Therefore God gave the laws and 10 commandments as rules for man to live by because man was now at this point corrupt. However He also made a way for man to be truly forgiven through Jesus. When Jesus came and died on the cross He took on all the sins that ever were or ever would be onto Himself. WE ARE ALL FORGIVEN now. The only way to not be forgiven is to just not accept His gift. So no stoning is not approved. The message Jesus taught was forgiveness and that we all fall short. Everyone has sinned and one sin is as another so if you have never sinned then I suppose you could feel free to cast the first stone. But even those in Jesus' day that opposed Him could not rightly do that.