Kenjaku vs yuki question

This fight was very cingusing to me so i have some questions please dont call me dumb ir say i have to reread:

What was tengen plan? Like he was going to do something to kenjaku domain but then the domain didnt had a barier so he couldnt do it and yuki couldnt use her domain and i dont know why either. I have a hard time understanding domane interactions and those stuf

How did kenjaku survive Yuki's black hole? And was that black hole the secrete techince kanjaku thought Yuki had???

Please help meeeeeeee!!!!