Did you ask on discord?
Practice mode is just what it sounds like. It allows you to practice without the lingering fear of being killed by Saiko-chan. Saiko-chan is still there, but she's basically like an early version of "friendly mode" except she doesn't get angry and doesn't give you medicine or anything. She CAN kill you, but it's only under very rare circumstances. So rare in fact I believe it's an oversight. I think it's when she sees you hide? I can't remember.
EDIT:
Habupain has put up links to old builds over on discord. Check them out over there~