FAQ
Is the cost of this Character card 11 when it is in my hand?
No, the cost of this card when in your hand is 7. The "This Character gains +4 cost." effect only applies when this Character is on your field.
I used the [Main] effect on "OP07-096 Tempest Kick" to give my opponent's "OP08-084 Jack" −3 cost. Can I K.O. "OP08-084 Jack" using this [Main] effect?
Yes, you can.