As we're unlikely to see terraces again at football, this is the virtual equivalent where you can chat to your hearts content about all football matters and, obviously, Arsenal in particular. This forum encourages all Gooners to visit and contribute so please keep it respectful, clean and topical.
From my understanding, both list A and B will be able to play in the game. List B is basically the youth players that under UEFA rules do not have to be registered as long as they meet the criteria of "being born on or after January 1, 1990 and has been eligible to play for the Club for an uninterrupted period of two years or more since his 15th birthday."
The whole 'can only change one player on list A' is if we, for example, buy a 27 year old from Italy who can not fall under list B and so will be have to be placed in list A so we'd be allowed to bring him in and make one change to the list.