Blender: Clothes for model, Animations, World

hi Izura. possibly able to answer your several questions.

1) bind clothes and hair to "blank(naked)" model
first, get .blend file of clothes/hair what you want to wear, combined all mesh layer and save.
second, open "blank" .blend for make pose, append clothes/hair's combined mesh object into it.
third, at clothes/hair mesh layer's "modifier" tab, change "geom_skin(armature modifier)" object target to "rig".

and I'm sorry I not know the way of load sim model to Blender. I guess that body/face shape of sim managed by the bone what prefix "CAS" attached and these data is stocked somewhere in "Tray" folder.. :-/

2) separate, copy/paste animation
so, you want to delete animation data from model(armature)? if it's so, you can delete animation by the right click menu in out-liner window.
next, when you want to copy/paste animation(action) to other model, you can use "action editor(dope sheet -> mode:action)".

3) world
"world"'s color setting is in the theme setting(file -> user setting -> "theme" tab).

I think your question is more relate with Blender. If you'd like to find more detailed, maybe you can find an answer in Blender's forum/reference.
cheers!