Identification of a Buddhist text written in classical Chinese or Japanese
It is classical Chinese written in part of Chinese character and part of Japanese kanji Character,  it is still Chinese text, I can identify it because I am a Chinese speaker.
Yes it is Lotus Sutra
Kumārajīva and Yao Qin translated an ancient book "龜茲文本" to Chinese, that is Lotus Sutra 


I can only answer this, I have no information for the rest of questions