Answer:
"fs la /mit/joeuser"
or
"cd /mit/joeuser; fs la"
Answer:
"fs sa /mit/joeuser janeuser rl"
or
"fs sa /mit/joeuser janeuser read"
Answer:
"fs sa /mit/joeuser system:students rlidwka"
or
"fs sa /mit/joeuser system:students write"
Answer:
No. AFS ACLs operate on a per-directory basis. It is possible to have two files in the same directory and, for example, remove the UNIX "write" bit from one, but anyone with AFS permissions could restore the access.
Answer:
"fs mkm /mit/username/MyBackup user.username.backup"
You don't need to "fs rmm" the old mountpoint, but it also doesn't hurt.