Does anybody know if you car get the stallion race car, duke o death and whatever else online? 
Dukes only in single player for now. The next Gen version of GTA is so fking fast at loading stuff, that trying to hurry and go to a different screen to attempt a glitch is impossible. I would say try doing the “get a car from single player to online glitch” from the Xbox 360, but those cars are only on next Gen. A money glitch for GTA next Gen has already been found, so that sheds light on the fact that there are more glitches to come.