Friday 23rd.
We were thinking Huddersfield to Piccadilly to Levenshulme.
Walk, via hostelries, to Burnage.
Then Burnage > MAN > HUD for the return.
You wouldn't be allowed to go via Piccadilly to Levenshulme on your ticket. The only option would be taking the 1 hour rail replacement to Stockport, then getting a service to Levenshulme.
If you put in your ticket info (Huddersfield to Burnage) into the forum's site, then disable split tickets, and put in via Levenshulme (or just
click this link), you can see the valid itinerary it generates for a Huddersfield to Burnage ticket:
Huddersfield to Stockport rail replacement
Stockport to Levenshulme (where you'd stop short)
Levenshulme to Manchester Stations
Manchester to Burnage
Despite the tickets costing the same, it's not valid by default, and it's up to you to hope staff would be pragmatic about the situation if you chose to go via Piccadilly. An excess wouldn't be suitable, I don't believe, as it's not a change of route, nor over-distance as you don't even pass through Burnage to get to Levenshulme.