It is the large bridge east of Castelia City, you can access it only after you defeat the league champion.
In Black 2 as well as White 2, Skyarrow Bridge opens up once you've beaten the Elite 4 and the Champion.
In Pokémon Black 2, Pinwheel Forest is located South of the Skyarrow Bridge and West of Nacrene City however Pinwheel Forest is inaccessible until after you beat Iris, the Pokémon League Champion due to the Skyarrow Bridge being blocked off until you've beaten the Champion.
You can finished the game, but now you can visit southeast Unova by going across Skyarrow Bridge.
Yes, you have to complete the game, ie, defeat the elite 4 and the champion. Doing so will unblock many exits, letting you go on Skyarrow Bridge, into Twist Mountain, to Icirrus City, etc.
It relates to the ghost in pokemon white 2/black 2 where she haunts the strange house and in it is the lunar wing and then cresselia will appear on Marvelous bridge if you have the lunar wing.
You need to beat the Elite 4, and access it through the Sky Arrow Bridge (and head down) before you get to it.
It is Cresseliayou meet Cresselia after the hall of fame in pokemon black+white 2 you need to retrieve the lunar wing first from the Strange House near Reversal Mountain. then go to marvelous bridge and you will meet Cresselia
Black Kyurem is in Pokemon Black 2.
There are 3 chances to get it: 1. From Route 11. 2. From Village Bridge (White only!) 3. Evolve Rufflet to level 54.
Yes, you do have to beat the Pokémon League which includes beating the Pokémon League Champion known as Iris until to go to Nuvema Town in Pokémon White 2. You will not be able to enter Skyarrow Bridge until you are part of the Hall of Fame for defeating the Elite 4 and Iris.
Pokemon Black 2.
No there is not a trainer editor in Pokemon black 2 or Pokemon white 2