Have it checked over by a good gun smith.
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.
As a general rule, NO, NO, NO!!!!
Assuming it is in good condition to shoot any modern day ammo, yes.
If it's a modern .30-06 rifle, yes.
12, 16, 20, 28 gauge, or .410 bore, depending on what it is chambered for.
If you mean Taylor's & Company guns, yes.
DO NOT ATTEMPT TO SHOOT MODERN AMMUNITION IN THIS WEAPON WITHOUT HAVING IT EXAMINED BY A GOOD GUNSMITH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Danger, Danger, Danger
You should be OK with standard loads.
DO NOT ATTEMPT TO FIRE UNTIL EXAMINED BY A COMPETENT GUNSMITH!!!!!!!!!!!!!!!!!\ Danger, Danger, Danger
It is difficult to find even 10 gauge shotgun ammo today. I have my doubts if 8 gauge shotgun ammo is even made any more, but corrections welcomed.
Any modern ammo should be fine. Your barrel should indicate whether you can shoot 2 3/4 or 3" shells. You may want to consult a gunsmith to see if you are able to shoot steel shot through your barrel or not.
Have it checked over by a competent gunsmith. Good luck finding ammunition.