Don't know, but I wouldn't have thought so, they're not the same job, though jannies may well clean up outside a building. :)
Not really, no. Cleaner, not a janitor, the latter typically has fairly broad responsibilities that may include cleaning, whereas the former cleans.
Cleaner as in dry cleaning? "Take this to the cleaner's."
Put the apostrophe on the wrong side of the th' and marked wrong :(