Answer:
11. "like a leopard's tawny and spotted hide, stretches the plain to the dry grass and the drier grain." a leopard's hide is being compared to how dry the grass and grain is.
12. the author is joyful to have the rain because line 2 says "After the dust and heat" and line 20 says "to the dry grass and the drier grain" so the rain is here to finally make it less dry
13. the author's outlook affects the poem in a happy tone. as we see line 5 says "How beautiful is the rain!" we can see that the author is happy and excited. but, rewritten in a non expressive tone, "How beautiful is the rain." sounds dull or even a questioning tone: "How beautiful is the rain?" is a questioning tone which would be the author wondering how beautiful the rain is.