Yes it is a metaphor because he does not literally have a key to her heart. It is just figurative speaking.
Answer:
Alyssa is so Impassive that her friends never know how she is feeling. *
Memorandums. a memorandum is a written message or record made for future use and is especially used in business or diplomacy.
Answer:
Don't do it because it's not good of you to do something dangerous
The theme is that planning may result in less fortune than what chance may result in.