> Aand lastly, Airbnb decided to just void a 500$ giftcard that I got in 2018 and I tried to use early 2020 and they said it was invalid, I just lost the money.

If this was in California, gift cards cannot expire (with some exceptions). You might have a recourse there.

https://www.dca.ca.gov/publications/legal_guides/s_11.shtml