The fallen angels do. (The ones that followed Lucifer known as Satan)
No. The good angels do not sin at all, they always do what is right.
mortal sin
God does promise victory over sin. This is from the Bible.
Calvinists believe sickness is a sign of gods displeasure with you for some sin
The angels and the greek gods
worshiping other "gods"
Blasphemy
A demon is a jinn. Jinn are made of smokeless fire (plasma), they have freedom to pick sin if they please. Angels do not have freedom to sin, they happily worship and follow God. The angels were made out of Light.
gods grace gives you the ability to be forgiven for your sin. you can still sin though you just have the privelage of being forgiven
In Christianity it doesn't matter what sin you commit its the same as any other sin for example to lie is just as bad as murder in gods mind.
Yes, the Bible gives several accounts of angels sinning, i.e. Lucifer and his fall from Heaven because of his pride and greed.
No because in the bible it says "All man will be judged for his own sin".