Does anyone know if you can open a QB 2021 Mac desktop file on QB 2020 for Mac?  OR:

Can anyone tell me where to buy a license for QB 2021 for Mac?  I converted to QB Online and hate it.  I downloaded QB21 and have managed to get everything back up to date but now need to buy a license.  I've read that Mercari is a likely scam, but can't find it anywhere else.  There are some folks selling the 2020 version.  I'd even take the 2016 version as I also have that.  It's just a function of "downgrading" the file.....