1. Ball should ALWAYS loop behind the mini playfield in normal non mode play, and Yokozuna play. The diverter is only active when the ball needs to be routed down center ramp, as in starting multiball mode, collect jackpot and a couple other modes like belt rounds and such. I had to adjust my diverter when I first got my WWF because even in a non active mode, enough of it would barely stick out and knock the ball down the ramp and not allow it to loop correctly. Another fun issue is that if you adjust the diverter too much to allow for correct looping you can actually cause another issue. Fast ramp shots will actually run the ball past the diverter before it has time to correctly divert the ball down. It's a touchy diverter but once you get it right it makes the game play much better.
2. Tag Team, I don't remember much since it wasn't often a 4 player game was available but I think it's just an automatic feature that really can't be turned off or on. It's just there, the scores are still seperate, but if I remember correctly it also simply displays a combined score along with individuals but nothing special changes about the gameplay at all. I no longer have my WWF so someone would have to check that one to be sure.
3. Highly underated? Ding! Ding! Ding! Most definetly. I've said that I would probably not buy a machine back that I've already owned but this one I would. Regreted selling this one alot. I'm an 80's fan of wrestling so that helps. Even with that, the gameplay is really alot of fun. Ohhhhh YEAHHH!