Looking to see if anyone has had experience and success stories of upgrading from economy to executive class via check in or at the gate with the fixed fares published on their website? I contacted their customer service, but didn't feel very confident with their responses. Any experience specific to YYZ-LIS return will be most relevant for me.

Main questions I wanted to have answered:

1) If there are executive seats still available (will be tracking via experflyer) at check in time, do all seats open up and available for upgrade purchase at the fixed price (ie: $489CAD)
2) Does the upgrade option show up through check in online (like Air Canada often does) right when check in opens up at 36hours.
3) If this option only works in person, can I show up at the airport 36hours in advance of my flight and request this upgrade or is the upgrade time actually only available on the day of departure when check in agents are at the counter (ie: 3hours and 30mins prior to flight - I got this time based on when hold baggage drop off counter opens up as per TAP website)
4) Do the same rules apply when departuring from Lisbon as above.

Thanks in advance!