The devil was a angel with free will, who sinned and fell from his glory.
Now the devil tempts us to do evil etc...
Kyas why do you ask such questions? what religion are you?
Instead of asking all these questions I actually suggest reading the Bible.
Read it first, then ask questions. Maybe you have read it but it seems to me you havent, as you would be able to answer the questions you ask on your own.
Peace