Look at the sky, it might snow
Snow in this sentence is the verb.
Snow is a noun in that example.
Yes, as in: "Will it snow in December?"
yes
The word fell is superfluous in that sentence. I would say, the snow covered the fields like a blanket.
Since it modifies "shovel" it is an adjective.
The simile in your sentence is "like roses".
Mountain
It's a noun.
The word "cold" is the adjective in the sentence. It describes the type of wind that is blowing.
Snow is white.
"snow" is a verb.