FJ didn't have anything like that, just the whole area in general was opened for the public for a certain amount of time before the official opening. That's how I remember it at least. However, as Mac said, I noticed some days it would be not available. Probably not only due to needing to fix things up (as I remembered the ride did sometimes break down, or stop briefly during the ride a lot), but also due to the massive crowd.
I would imagine it would be the same thing for Kong. You just never know until you're there and word of mouth spreads the news, or someone is willing to perhaps post about it on here, but like has been said in other posts, it can stop whenever. It may happen one day, stop the next, or even the same day.