Only use a double-sided shader if you don't case about how the other side looks, because as GlowingPotato said, the vertex normals on the new faces are going to be default angles which means the normal map won't be transformed properly on the new faces. Also a double-sided shader should be confined to only the faces that…
1) i think that using a double sided shader, you will have wrong lit in your leafs. I may be wrong, but in my opinion duplicating the mesh and reversing the normals should give the best results. The you can tweak those vertex normals to have a better lit. 2)Humm, If is not dynamic, i would approach by placing joints chain…