You know that OST album of EX3 doesn't include every tracks from EX3 game. Especially the ones from old EX album. But when i listened them again today, it seemed a kinda different from old EX1 Arrange album and EX1 Plus Alpha Game Rips. Am i right about that they are really arranged again for EX3 or is it just my imagination?

Not really sure I understand your question exactly, but here's how the music is presented:
The stage music is all originals.
The characters exclusive to EX3 all have original music.
The reused characters use the songs from EX+Alpha PS1 and EX2 PS1. These fighters songs aren't remixed, unless you're comparing them to the arcade or arranged albums. The PS1 music was a third version different from the OST & ASTs. Hope this helps.

yeah,it really helps.thanx!