Well i had to do it 5 times because Cresselia always got beaten.He is strong but if you are on a high level(at least 60-70) you shouldn't have much trouble.
you have to beat darkrai then wait afew days
evolve your main characters and try to "join 'em all"
defeat darkrai mission
70 or higher
You can recruit legendaries and do more things.
first beat the guild exam then u'll unlock luminous spring it'll say u can't evolve beat darkrai and then recuit manaphy and then unlock marine resort.
You have to beat palkia the second time
Just like Pokemon time and darkness you cannot evolve until you beat darkrai. If you also need an item you should get that. But be warned you can never go back to your previous evolved form. I have Pokemon darkness and sky. My brother has time so I know a lot about the games. You also have to recruit Palkia.
You can't actually beat the game, but the farthest you can go is defeating Darkrai. You can be considered beating it if you beat him.
beat darkrai for the last time.
yes
Then you have to beat Darkrai.