sorry it does not
They are two seperate engines so no.
Hell no
Nope.
Yes it is exactly the same as the multiplayer for Red Dead Redemption
Go into multiplayer free roam press select then go to undead
its on Undead Nightmare
yes the multiplayer works but the single player is only undead nightmare
You are unable to play multiplayer on Red Dead Redemption without an internet connection.
No. Undead Nightmare standalone disc is the Undead Nightmare, Legends and Killers and Liars and Cheats packs (possibly Outlaws to the End too) + Multiplayer. There's a possibility your multiplayer lvl from RDR carries over when using the UN disc. I do not know as i have RDR and the UN download for Xbox but the UN disc for PS3
You can't play coop on Red Dead Redemption or Undead Nightmare.
You cannot play multiplayer mode without internet connections.
You cannot get Red Dead Redemption - Undead Nightmare on the PlayStation Portable.
No, if you buy the one for 20 dollars that is undead nightmare but not the original. The only way to get both is buy the Original Red Dead Redemption and then buy the Undead Nightmare add-on
Just go onto multiplayer and join a free roam session.
No you cannot join with the zombies in undead nightmare