I
believe they are both possible. A almost certainly, B is a highly likely...
The restriction on a Single Tickets and ONLY the Outward Portion of a Return is that the journey needs to be completed in 90 minutes. For some journeys a change of Tram is required so effectively a break of journey could be done.
Take Piccadilly Gardens for example, You may wish to change Tram there but whilst waiting want to pop across to the Bus Interchange to check or collect a timetable. If the journey A - B (Maybe via G) is completed in 90 minutes it's valid
AIUI▸ .
Also the fare between Piccadilly and Harbour City is the same as to MediaCityUK. I believe the prices are done on fares.
I recently did a journey on the Metrolink (Shudehill - Piccadilly) Yes I know I could've walked but for ^1.10 I couldn't be bothered. But my ticket has the following:
From: City Zone
To: City Zone
So if you abide by the 90 minute time limit and say within the zones for which you've paid, I'm sure you'll be fine
Here is a link which gives you the prices between two points:
http://www.metrolink.co.uk/tickets/Pages/ticketselector.aspx