Questions about Japanese language?

Question:

I have a few questions about Japanese as I'm writing a story about a Japanese girl but I don't know anything about the language..

First of all, is the writing different to spoken Japanese? Like, can you be able to speak Japanese but not write it? I think Mandarin and Cantonese is like that?

Also secondly, if you were addressing your daughter, do you just call her by her name? Or do you add something at the end? Because my main character is called Katsuko, so if I was addressing her as her mother would I just call her that?

Please forgive my ignorance...
Thankyou so much for your help :)

Answer:

1.No. You need to know the Japanese alphabet to sound it out (Hiragana, Katakana, Kanji) But it's better to have both it what I'm trying to say.

2.Yes. But be aware that if in your story, she is talking to other people, use honorifics, such as calling someone from their last name.

Sana or San is the most commonly used honorific. (Mr. Mrs. Ms. is the closest English Translation)

Chan would be used for babies, little girls, and teenage girls.

Kun is generally used for boys, but can be used for close family friends.

Sama is the respectful version of San.

Sensei is teacher, doctor, politicians etc.

Respectfully, you would have to call someone by their lastname and the above honorifics after, but for very close friends, you may just call them by their first name.

Here's some examples.
A girl named Yuni Nakamura will be the name, and her son, Tom Smith.
Yuki Nakamura as a teachers, doctor, politician etc : Nakamura-Sensei
Yuki Nakamura a little girl : Nakamura-Chan
Yuki Nakamura as a mutual friend or someone older-Nakamura-San
Tom Smith as a friend: Smith-Kun
I hope I helped! :)