Earlier quoted context omitted.
I never considered how a Chinese speaker (writer?) would deal with a foreign language that doesn't have a written form. What did they do in 950AD? Surely there's some way of transcribing sounds in languages like Chinese for foreign languages.
In the case of Japanese they went through two phases. First they developed a phonetic alphabet specifically for Japanese https://en.wikipedia.org/wiki/Hiragana then in the next 30-50 years or so they developed the system that we know today which use the kana in a secondary role. In Japanese, for instance, you tend to put the verb at the end of the sentence and the “stem” of the verb is usually written in Chinese char…
No. First they used a set of existing Chinese characters that matched the syllables of Japanese - https://en.wikipedia.org/wiki/Man%27y%C5%8Dgana
It took several hundred years until Hiragana developed from the cursive writing style of the Chinese characters.