1. Is this correct (grammatically)?

I bought bananas, strawberry, honey, and some books. ( also are the commas placed correctly?)
(And do you call punctuations in English mechanics?)
2.Do I use the word "had" to emphasize something? Ex: The communist had transformed their country.

1. Your commas are correct. However, it should be strawberries (plural).

2. We use "had" to show an action that occurred in the past and no longer is occurring.