When I've played, I just couldn't get the car to be AWD with a steerable rear axle. So no, it wasn't there since the beginning believing the guy above.
No. He's asking for BOTH AWD and 4WS at the same time. The 4WS in the pessima does not allow for AWD. Some real life cars had both at the same time, the 3000GT and the R34 skyline comes to mind.
Well, I have a mod that it allows me to have both AWD and AWS at a time. I can't remember what's that, WBIMP I guess. Btw, I'm playing on the 0.22, it's possible that it doesn't work on 0.23. Also, I think make a new rear suspension is not hard at all, you can add the rear diff slot to the original rear steer suspension, change the name of the suspension and change something in the information paragraph, then finish, you can drive a AWD,AWS car