Is there a substitute for mirin in a recipe?

You may substitute sweet Sherry, or dry Sherry if you add sugar since Mirin is a sweet rice wine.

Yes u can, but lime is also an option.

For one cup shortening use 1 cup butter or 1 cup margarine minus 1/2 teaspoon salt from recipe.

it depends on what your cooking

For one teaspoon of allspice use 1/2 teaspoon cinnamon, 1/4 teaspoon ginger, and 1/4 teaspoon clove