Hmmm, I'm not sure about your first question really. I mean, really if you want to include tidbits of the species, it's better to just put it in with the original post, but I don't see why you couldn't just tack it on in a reply to the character profile.
The second question of course is "Yes! Edit to your heart's desire!" That is your character, you change whatever the heck you need to change with it! Had a neat idea for a scar or perhaps a personality quirk? Change! Maybe during the course of role playing they had a little incident or traumatic experience and don't trust people or dislike pickles, go ahead and change! It's your character profile, you change it to whatever you need to change it to!