You can upgrade the data to 2022 or 2023 but as soon as you do the client would have to upgrade their program. The Accountants Edition can open Pro, Premium or Quantum but the data has to be 2022 or 2023.

To convert the 2012 data you would have to install the 2015 demo version and then open  the data in 2023 version. Once the data is open in a newer version you cannot go backwards.