You can unlock the special cup by doing the mushroom and flower cups, and then the star cup. It will unlock the special cup for you when you are finished.
The cornstarch/baby powder method will actually work on leather as well. You can definitely give that a shot if you don't have the leather oil remover.
Yes, of course. It has the same ratio, which is all that matters. You can double, half, triple, etc. any recipe, and will just end up with more or less...
The next safest surface would be a room with carpeted flooring. That way if you fall it won't hurt as much. Place pillows around you to soften any falls.
