On the free Melbourne tram: this program is only a few months old which is why you may be getting mixed messages on it. Trams are now free within the CBD grid and Docklands.
There is also the City Circle tram which has been free for many years, but no longer has so much value now that all CBD trams are free.
The free tram zone doesn't extend as far as the Hilton South Wharf, you'll need to cross the river. There's signs around advertising the precise extent of the zone.
Of course if you're going outside the rather limited free tram zone you'll need a myki anyway, and if you make two trips more than two hours apart you'll already have maxed out the daily Myki spend, so the freeness of the tram may not be particularly worth worrying about.