3 Answers

Quote you: "I am not allowed to use a letter twice"

Are you allowed to cheat and ask others to do your homework for you? 

I will take pity.  I usually don't do this...

near  ace rear graph gone prone nape reap gone roan groan cone phoney phone.... then you get the digital version of scrabble and plug this word in...I didn't tell you that... good luck and shine tomorrow.

Homework? Are you kidding? It was the most interesting game of my youth during the traveling. I'd like to have a teacher like yours :) Unfortunately, English is not my native language, so my vocabulary is very poor, but here are my words:

hear, ear, nap, ocean (of course), hype, honor, poor, con, harp, rap, can, gean, crop, pony, etc ;)