They probably would taste sweet, but I wouldn't recommend eating them the point of sweet peas is that they look and smell good in the garden, eating them is surely not an option !
Sweet potatoes are not actually sweet. They are called sweet potatoes because they are not bland, and people back in the day had never tasted such a good potato before. Because they considered candy...
I'd say it is. Repetition is something (an idea, a word, a phrase etc. etc.) which is REPEATED for effect. Here, the word 'sweet' is repeated. It is done for effect. Hank Williams in one of his songs...