Her sleeping only 3 1/2 hours is limited to when she is on her rehearsal schedule, I believe. Judging by some backstage clips, she does take naps between shoots and such to catch up on her lost sleep. It's not healthy to have so little sleep regularly so I think she does find the time to catch up on it.

As for her home, I'd wager it is a multi-level apartment or it is one that takes up an entire floor. She hasn't mentioned at any point where she lives or what type of set-up her home is, or if she has more than one home. I'm not sure what the norm is in Japan but it would be unlikely she has more than one apartment. She keeps mentioning that when she goes places, she always brings her own bedding and such.