A flat character is someone is unchanging throughout the story, in other words, the character is Stagnent.
Rhythm...................................................................................................
The speaker had a specific identity. He was A.H.'s friend and this was the way he mourned him. No one else mourned him with those words. No one else shared the same experiences with A.H. The I may be known to the reader but that doesn't matter. The I is expressing his personal grief in his poems.
It means that its always lined up
Either the 2nd or 3rd bullit point