No it is not, it is only multiplayer online.
do your missions
you cant
Whatever you want
Go to on line as usual, and go to your challenges and pick undead overrun.
as of 16th September 2012, £7.99 in the United Kingdom
you can get a knife in multiplayer i dont think single though.
personally i believe that red dead redemption is better as it has a longer story mode
Yes you can once you have downloaded the extention
It is some we're in the bush around thieves landing
yes
yes you can but you must first download it from the playstation store or the xbox equivalent
Tall trees great plains any where really