1. Is there any possible way or option to replace a characters over character I don't wan't to use in the game?
2. Is there any possible way or option to delete character from character page I don't want to use in the game?
Not currently. There is a tracker entry, however: http://www.adventuregamestudio.co.uk/tracker.php?action=detail&id=161
As far as replacement goes, yes. You can enter in a new name on the character and change the views, etc to new sprites.
But everytime I want to import a character a new character will be added on character section. I just hate it when that happens. Of course I could rename and change character but if I only want to have two character in a game instead of three characters the third character will then be unneccessary for me. Just like if I have changed my mind having a dialogs it is still there and I can't delete it off.
BTW I thought this question was deleted until I saw this thread. Lucky me. ;)
I agree that this is annoying -- as strazer says it's on the to-do list.
Thanks.