Can a 31 inch tire go on a 30 inch rim?

No. The 'inch' figure for tires is related to the diameter of the interior 'hole' in the tire while the figure for wheels is linked to the outside diameter of the wheel. Trying to fit a 31 inch tire on a 30 inch rim would result in a 1/2 inch gap all the way around between the tire and wheel.

Cheers