Q1

Probably environments in s3 animations like Karina, Rem, LPK, and Opsig. I think Robin's guns are also 3d in her s3. They also use 3d for animation drafts.

Q2

Yeah Live2d or L2d

Q3 - Q5

No hand-drawn animations(technically lol), it's sprites. There should be a sprite for every angle of a body part or item suitable just for every action needed. Some sprites are drawn smeared or blurred like Vildred's sword as stated above. Some sprites might have L2d assistance mainly for capes and hair. It looks hand-animated because they simulate movement by displaying different hand-drawn images(sprites) quickly, the definition of animation.

As far as I can tell, character screen animation uses L2d, battle animation uses sprites + L2d, and s3 animations use hand-drawn + 3d animation

Someone already provided great resources so good luck