no
Defeat Darkrai then cresselia will be outside your house talk to her she will join your team.
I looked it up, you can get Cresselia, but it doesn't say how. It only says you can get Cresselia at Sharpedo Bluff.
Home
No you do not. You see manaphy's egg in a dungeon after you save scizor and it hatches the next day. You then have to feed it and save it.
after doing the darkry mission in dark crater, creselia will be waiting by your house/den. talk to her and she joins you
cresselia
Darkrai is at the Dark Crater. You will have to go with Cresselia (you can do this after you graduate from the guild) then he will warp and he will lose hes memory he appears i9n random dugeons
After you beat dialga there are several things you must do. If done Cresselia appears in your dreams a little while after Cresselia appears you have to do a few things then the night you talk to Lapras Palkia appears and takes you to Spacial Rift.
unfortunately no but he's in darkness
You should beat both stories and get Palkia, Diagla, and Cresselia on your team.
well we can't but you can battle palkia! he is in special rift
Eventually, actully a long time after the main story, you will meet him and he will tell you to meet him in dark crater. Cressilia will take you there. There is 14 floors and then a rest spot, and then 15 floors then darkrai. Dont let cresselia battle him though- she has a type disadvantage.