Gen'yumaru.
orochimaru's arms get healed but then he ends up dying
He wanted Tsunade to fix his arms. However, she betrayed him, so his arms never got fixed. Instead he took over a new body. That's how his arms are alright now. This happens in the end of naruto, a few episodes before the time skip to shippuden. Orochimaru intended to take over Sasuke's body, but Sasuke arrived too late. He takes over another body instead.
The body will heal around metal plates because the plates cure the body
Yes.
no, the arms mend faster
Your body creates scabs to protect the inside of the wound/sore from infection so it has time to heal
Yes, all parts of wolverine's body can heal
no they do not
Wait for the body to heal itself.
Nothing but what you have been told to use by your professional body piercer. There is no secret heal fast cure, it will heal as quickly as every other injury to your body and old as quick as you allow it to, so don't mess with it and it will heal.
you don't need air to heal. your body has many different hormones, chemicals and cells which work together to heal areas. these use the blood vessels and lymphatics to move around the body! is this what you mean?
brain