Revelation 21:8 (New International Version, ?2010)
8 But the cowardly, the unbelieving, the vile, the murderers, the sexually immoral, those who practice magic arts, the idolaters and all liars?they will be consigned to the fiery lake of burning sulfur. This is the second death.?
Whether or not a certain group consider it's a sin or not, it's foolish to just "toy around" with anything you're not well educated in. You could wind up with no benefit, at best, and at the worst you'd find yourself in a world of trouble.
As long as it's not used to further evil purposes (things that are normally morally wrong), raise/speak to the dead, or just plain superstition, it's fine. Those are the contexts every verse in the Bible that speaks out against witchcraft contains, at least in the original translations.
Yes it is ,Where do you think that power comes from ? what if those two spells work and what is to stop you from being tempted into doing more ? James 1:14 "But every man is tempted, when he is drawn away of his own lust, and enticed."
Yes it is a sin, to do any divination according to the Bible. That is Satan's work.
Christians are to do ALL things for God's glory. The Bible says you cannot be partaking the table of Jehovah and the table of demons. Demons are only going to do harm, and that would also be idolatry.
Jesus told Satan at Matthew 4:10...'It is Jehovah your God you must worship, and it is to him alone you must render sacred service.'
You don't really seem to understand what Witchcraft actually is.
Witches / Wicca / Witchcraft (whichever term they prefer to go by) is a valid and legitimate religion. It is officially recognized by US law as a real religious belief system.
So now that you know what it is, your question will now seem rather foolish. You're basically asking if it's a sin to practice another religion for fun. You can make up your own mind on that one.