Unusual question about unlockables

[Jamie Goode]

Hi all, Just wondered about unlockables, can you obtain them through the challenges? Like the stay undefeated for a season? Also if you play FMC with two players does that stop you unlocking any of the unlockables? As in you start with one, then lets say you add another for a big club like mancity and try to buy a player you bought? [the unlockable for selling a player for a higher fee than you bought him in?]

Thanks in advance, jamie