Three separate codes - any, all or none of them might (or, more likely) might not work.
The text said 50% of all fares: very clearly this was not the case.
Term and conditions in both Portuguese and English text said 50% off fare except airport charges. Clearly (again) this could never be the case: taxes and duties are inescapable. YQ isn't mentioned.

Hey, it's TAP. I'm sure it's not an outright scam, just a marketing initiative badly implememted. TP's not a carrier known for transparency, customer service or IT sophistication. They have had some bonkers low fares though, and if these were mistakes- it's to the airlines' credit that they let them stand.