Why is the poet talking about separation in the poem? Is this a one-sided love? Or has the beloved betrayed the persona?

A red , red rose is a poem written by Robert Burns as He was a romantic poet, his poem explains his love towards a girl he saw. That was his love at first sight. He dedicated this poem to her. He talks about separation as they are far from each other and it was a one sided love.

Which figurative language is used in the poem? Explain with examples. 

The theme of "The Gift in Wartime" is to mourn the sadness and futility of lives lost in war. In the poem, the speaker, who has to faced the death of her beloved husband in a war, speaks directly to him, contrasting what she has offered and what she received. 

In the poem, many figurative speech such as irony, imagery, anaphora, apostrophe are used. Irony takes place when the poet talks about the gift which is not a real gift but is infact grief and loss and sorrow. A grave and shrapnel...

 To which two things does the speaker compare his love in first stanza?

The speaker compares his love to a red rose and melody  in the first stanza.