I'm assuming it has something to do with him being handicapped. And welcome!
cant move
Why? There's no explanation in the manga
yeah it's because of this because with all his powers in one body he's almost invincible xd
Remember when the rods went into his back due to him using Demonic Statue of the Outer Path to kill hanzou? That made him basically immobilised and he wasn't able to move freely.
He prolly just made the bodies for two reasons. 1. He was crippled during a fight of some kind. (which is the most likely) and 2. It reduces the risk of him dying to almost 0.
Hanzo killed his legs.