Generally, someone who teaches truth, points people to Jesus, encourages sound Scripture-based practices, and in whose presence "miraculous" things happen is someone who should not be judged as false. By all means withhold judgment while you look for good fruit, but don't reject something as "not of God" just because "miraculous" things occur (which some here are prone to doing!).
Further, don't judge something as "anti-biblical" or "anti-Christian" just because there isn't an example of it in Scripture; that's not a valid criterion. Nowhere in Scripture does it say that God will never do anything other than what is already recorded (indeed, if it did, it would have to be the last words in the book!). Again, that's not a valid criterion.
If and only if someone is teaching falsehood, pointing people to false gods, bearing bad fruit, or doing things that are clearly anti-biblical should we conclude that their ministry is not "of God".
By the way, falling backwards (in and of itself) is NOT a sign of demonic activity. Let's remember that we are not to judge by mere appearances.