Depends on when it was made.
It will shoot any type it is chambered for.
yes.
Unless specifically mentioned in the owner's manual not to, yes.
No way to answer without knowing how old the shotgun is, what the 00 buck is made of and the choke of the piece.
You will have to call Browning to find out.
100-600 USD, depending on model, condition and accessories.
You must contact Browning for the answer so you don't void your warranty
Yes
A 12 gauge shotgun cannot fire 20 gauge shells.
No, you can not shoot anything but 12 gauge shotgun shells through a 12 gauge shotgun. Never use any ammunition other than what the firearm was designed for.
You could eaither shoot dove with a 20 gauge shotgun or a 12 gauge shotgun. You should also use a bird shot shells