Well, typically in the official canon, Harry is not Voldemort's son. Fanfiction, however, allows for all sorts of unconventional storylines. So it's possible in a particular fanfic, but it's not the norm.
It depends on the context. If it's meant literally as a wife celebrating while naked, it's generally not appropriate in a public or family - friendly setting. However, if it's a more metaphorical use of 'birthday suit' to mean something like being in a natural or unpretentious state while celebrating, then it could potentially be okay, but still a bit strange - sounding.
It also improves Naruto's skills a great deal. He becomes better at combat and using his ninja techniques. For example, his Rasengan might be more powerful or more easily controllable after Iruka's training. Moreover, Naruto's confidence grows under Iruka's guidance. He no longer doubts himself as much and is more willing to take on challenges.
Well, 'in her birthday suit' is an idiom for being nude. So if there's a story about a wife 'celebrates in her birthday suit', it could be a rather inappropriate or just a very unique and private kind of celebration story. However, it could also be a misnomer and not actually mean being naked at all. Maybe it's a creative way of saying she's celebrating in a very relaxed and unadorned state, like without fancy clothes or something.
Well, in the fanfiction, Iruka may be protective by constantly checking on Naruto's well - being. He could ensure Naruto has enough to eat, is getting proper training, and is not being bullied by other villagers. He might also be protective in the sense that he gives Naruto extra attention and guidance in his ninja training, more so than he would for other students.
Iruka's teaching is more traditional, focusing on the fundamentals and the proper way to do things. In contrast, Naruto would be more about inspiring the students through his own story. He might say things like 'I was just like you once, and look at me now!' His style would be more about motivation and showing that there are different paths to success in the ninja world. Iruka would be the one to correct the students' form and ensure they understand the basic principles, while Naruto would encourage them to break boundaries and think outside the box.
Iruka influences Naruto's early development by being a positive role model. Naruto looks up to Iruka and wants to be like him. Iruka's kindness and belief in Naruto give Naruto the confidence to start believing in himself.
Iruka can be a great source of emotional support. He can listen to Naruto and his family's problems and offer advice based on his own experiences. For example, when Naruto is stressed about his Hokage duties, Iruka can remind him of how far he has come and that he can handle it. Also, Iruka can teach Naruto's kids things that Naruto might not have time for, like the history of the village in more detail.