Well, the guidelines of this website allow for one question a day, but I can try to help you with at least one of the questions that you posed.
I can help you to find examples of similes and metaphors in the poem "Mending Wall". Metaphor is when you compare two things that have similar attributes. For example, in the poem, Frost compares the shape of some of the rocks that have fallen out of the wall to "loaves" and "balls", which makes it difficult for them to put them back into the wall, because of all of the rounded edges. They won't stay put. He says to get them to stay, "we have to use a spell to make them balance." It is not a literal spell; he is just saying that the balancing act they have to do is similar to chanting a mysterious spell it is so difficult, which is another metaphor.
Similes are the same as metaphors, just comparing two things to each other using the words "like" or "as". Near the end of the poem, Frost describes his neighbor hauling huge rocks, and says he is "like an old-stone savage armed." The image of his neighbor carrying a stone towards him makes him think back to days when savage men used rocks as weapons against each other; it just affirms his feeling that walls are uneccessary and outdated in their world.
I hope that those thoughts helped; good luck with the poem!