Hey

I'll try my best to answer these questions according to what I understand!

1). Zetsu was a Hidden Grass Missing Ninja an entree to Akatsuki, of course only Tobi/Obito knew his origins, However, Zetsu needs a validated story to cover his tracks towards other members of the Akatsuki. He played spy.

2). Thanks for reporting the forum bug!

3). It's just game balance in a sense. Kusanagi was used directly in OG Orochimaru, however, Konoha Traitor doesn't use it directly if that better explains it.

Hopefully, this helps! Sorry if I couldn't answer what you were expecting.