"Has Hoshino stated whether or not Miranda will be taking a more active role in the future, or at least appearing more?"
Hoshino has mentioned that she needs to move on with Allen’s story at the moment, but would probably have Miranda run into him and start worrying about him.
"How do you know Jiji kissed Kanda first?"
It was written in the D.Gray-man Reverse Novels, in the third book, chapter one.
"Is Cross alive?"
Hoshino has made no comment on whether he survived the attack or not, but has stated a younger Cross will appear when the fourteenth’s story will be revealed.