#1 what do you mean exactly ? if you unlock one char, you HAVE TO play with it to unlock the next char
you don't get bonuses on chars exepted diffirents and better stats than a feeder
and you get more guild points by unlocking them
but you don't play the unlocked char on that char ( say you play mage when you unlocked samy on this char ) then even if you pass, you won't unlock the next character and you'll get only 1 gp
#2 yes you get 1 gp per fail
about the stats:
on feeder, for each fail, you get +1 stats
on samurai, for each two fails, you get +1 stats
etc..
so it is normal