@amal:
Thanks! No, each season the U-21 players are determined. Players have to be 21 or younger at the first day of the new season to be alowed to play.
About the tacts, i don't know that much about the stars and how its adding up. As far as i experience, individual skill of players is more important and a GK counts as two players. So investing in a good GK helps a lot in obtaining results.