If it was a mission through Wonder Mail you just have to re-insert the code, if it was a in-game mission I don't know if you can get it back.
You can't
there is a mission you need to do
In the Uproar Forest. To get this dungeon, you have to complete Wynaut's mission.
No, but you can only keep three with you on a mission.
sometimes if you finish a mission you can get a egg
yes but only if you recruit it or get it from a mission
mission recruit or egg
defeat darkrai mission
No
It classes it as a failed mission you lose money and some items.
go to buried relic
By talking to them in the dungeon the mission says there in P'S. Make sure you have click take job