1. Firstly, according to Spark Notes, the reason why the main character is called by two different names, "Shukhov" and "Ivan Denisovich" is because of social status For example, someone in a higher status, like a doctor or a guard, would call him "Shukhov" which is his family name because it implies more formality and distance between the individuals. Or, as Spark Notes claims, "The difference between “Shukhov” and “Ivan Denisovich” is the difference between cold official talk and cordial familiarity." Therefore, in the book, every time someone calls the main character "Ivan Denishovich" it might suggest that they are equal, meaning it might be another prisoner or someone whom he's friends/close friends with.
2. The narrative technique present in the novel is called Skaz, this style of narrative technique is usually present in Russian folktales making it easier for the reader to feel close to the characters. In the novel, the narrator is usually in third-person and a few times in first person, and that is because the author's objective was to make the impression that the narrator is an actual character in the story, although the narrator would be the very own Alekandr Solzheinitsyn.
3. The author wasn't only a novelist, but also a dramatist and historian. One of his life goals was to raise awareness on the Gulag, the Soviet Union's forced labor camp system. Unfortunately, it was very though for him to get his story through because of censorship at that time. Eventually, when censorship reduced, his novels were able to talk to people and raise the awareness he so dearly wished for.