You can just walk there from Opelucid, however you must have completed the game first, ie, been entered into the Hall of Fame at the league. That will let you access Twist Mountain to enter Icirrus from the west, and unblock Tubeline Bridge allowing you to get from route 9 to route 8 and Icirrus' east entrance.
aspertia city is the player's hometown in black 2 and white 2. you cannot go there in the original pokemon black and white.
That would be Castelia city.
Black 2 has Black City, but using the game's key system, it can also have White Forest.
Pokemon Black has Black city. Pokemon White has White forest
You have to use the Unova Link, and you can use the Infrared connection with someone who has Pokemon Black 2 (which has Black City), and receive the key from them.
In Nacrene city, the city after Striaton city.
no you cannot but you can battle latias/latios
There is no Cerlean city in pokemon black
Humilau city after beating Marlon
Talk to a guy in black city.
its a city in Pokemon black verison where the whole city is all black zekrommaster
In English, Hiun is known as Castelia City. It is the 3rd City you come to after leaving Nuvema town.