The appositive is usually a group of words related to a noun, usually a subject, and describes it in more detail.
The appositive here is a river that flows through Egypt.
Another way of easily spotting an appositive is by looking for commas - if it is separated from the rest of the sentence by commas, it is likely to be an appositive.
I do not get what question you are trying to ask sorry.
The poet is using a metaphor. Your answer is correct.
India was a British colony at the time
