Can you access the normal (without zombies) multiplayer free-roam using the red dead redemption undead nightmare disk, or must you use the normal disk? If the DLC's are on the undead nightmare disk, you must be able to access normal multiplayer free-roam fully from there, right? If not, how does the menu generally function with the game being split into two disks?

Is it comparable to (for example) MW2 on PC in which it shares one menu but you must change file/disk to play single/zombies and multiplayer?

Please be specific. Thank you in advance.