Ok great guide above but a few more tips for xbox one playing backward compatibility.
1. Join a party on xbox one for better quality for speaking :)
2. invite all players in party on the xbox 360 dashboard (entering gamertag) unless they are on your friends list
3. This can be done on pegparty private game (friends only)
4. The best character would be the bird with Zen ball thanks to the guys from my recent session all confirming this
5. the 3 not going for achievement use the super guide ability
6. 2-1 is recommended
The achievement is no longer glitched from what we have noticed :)