not that i know of
Yes and no, you can travel from the diffeent worlds that you unlock, but you must complete the task in a few worlds to unlock those other worrlds.
Clear worlds one by one.
By completing other worlds and the word appears you must open the keyhole to proceed
What do you mean unlock? They're free; they don't need unlocking.
There is no Poseidon Kingdom. There's Atlantica, the Little Mermaid's world, but like all worlds in Kingdom Hearts, it's opened just by making regular progress in the game. There are no secret worlds in KH, just secret endings.
About 12
Yes, it is the walls that blocked the world's in the Kingdom Hearts Galaxy filaments.
No. You must play the game and each time you complete a world, either another world will be unlocked or an event will happen which will allow you to gain access to other worlds.
I am on day 354, and there are 6 worlds (I think.)
Worlds are given to you in sets of cards. These cards are used to unlock a portion of your memory and visit various Worlds. However, there are certain Worlds that are eventually gained separately, not in the form of sets. You must progress through the story to unlock these Worlds. Here is a list of the Worlds in Kingdom Hearts Chain of Memories:World Card Set I-Traverse Town-Agrabah-Monstro-Olympus Coliseum-Halloween Town-WonderlandWorld Card Set II-Atlantica-Neverland-100 Acre Wood-Hollow BastionOther (Not earned in a set)-Twilight Town-Destiny Islands-Castle Oblivion
There will not be a Kingdom Hearts 3 for PS2 unless you mean Kingdom Hearts Re:Chain of Memories Release Date: December 2, 2008