Openssh - how do you disable "PasswordAuthentication" for a speci fic user

Hi All Q1. How do you disable "PasswordAuthentication" for a specific user, as I only want to allow PublicKeyAuthentication. Q2. Is it possible to user1@host1 user1@host2 as config setting for the "AllowUsers". (ie one account, but 2 valid hosts to login from). Q3. What options are available to limit a user to their home directory with out having to apply the chroot patch to Openssh. (i.e. they can't "cd .." backwards into the directory tree, but they can "cd .." forward in their home directory" Thanks in advance Steven