

If there’s a cost associated with having it attack, its controller isn’t forced to pay that cost, so it doesn’t have to attack in that case either. If the equipped creature can’t attack for any reason (such as being tapped or having come under that player’s control that turn), then it doesn’t attack.

You can move it any time you could cast a sorcery the equipped creature’s controller can’t. You still control Bloodthirsty Blade while it’s equipped to an opponent’s creature. There’s normally no way to have it attached to your own creature, although certain combinations of other cards make this possible.
