1. Does a minor demon token made by [card]Boris Devilboon[/card] work with the Ogres from CHK?
Yes. It has types "minor" and "demon".
2. Someone plays Eureka, can an opponent put a Control Magic on a Plated Slagwurm that someone else put out?
Yes.
3. Play a [card]Preacher[/card], Equip it with Lightning Greaves, Take a creature, Move the Greaves onto the Creature, Attack?
What's the question? This is legal.
4. Undermine a Blurred Mongoose just to make the player who played it lose 3 life?
What's the question? This is legal.
5. [card]Mijae Djinn[/card] fails the flip to attack after being forced to attack by a [card]Nettling Imp[/card]. Does it die EOT?
Yes.
6. Someone plays a sorcery during another players turn, and their Vedalken Orrery is disenchanted in response? What happens?
You resolve the cards on the stack normally.
7. A coin flip lands on the floor, does it count?
Not touching that one.