There is no order. It depends what missions you do first.
You can do missions for Bonnie MacFarlane in Red Dead Redemption, that is all.
yes
do your missions
Do your missions.
No, in undead nightmare you basically kill zombies and do zombie missions
you have to do missions
on the storyline there is 51 missions and 18 side missions
i have both and i believe red dead redemption is a lot better as on mafia a lot of the missions are very similar whereas there is a lot more variety in red dead redemption. also red dead redemption has a much better and interactive environment
do the missions which it says in your journal
You must complete the main campaign missions in order to get access across these "borken bridges"
If you want to be able to do this you need to complete the story missions on Red Dead Redemption and eventually you will unlock the higher levels of dead eye which allow you to use the X's.
there is no cheat for it, you must do the missions for it in your journal