JJ3 was started, then cancelled because they were making it without pay and were using the Unreal engine.

Jazz Jackrabbit Advance, a game for the Game Boy Advance, is kind of like a sequel. It is not really as good as the other games, but it is better than nothing. Best of all, it shows that there is still interest in Jazz Jackrabbit games and more might come in the future.

Asking for the JJ3 demo is illegal. It was never released, and is warez. It will just get this thread closed.