When Jesus died on the cross and the veil was torn, man was no longer seperated from a Holy God. Through Jesus the veil is torn and we are accepted as His children.
http://www.jesusdevotionals.org/2007/07/accepted-in-christ.html
What was the original sin of the Devil? Jesus said that He was a liar from the beginning. To see this we need to look back to the Garden of Eden with Adam...
Read more at http://www.jesusdevotionals.org/2007/08/sin-of-devil.html