ASA and Firepower reimaging
Cisco ASA devices can be reimaged between the ASA image and the Cisco Firepower Threat Defense (FTD) image. This is possible on models that support ASA software and FTD software.
Cisco has a guide that shows how this can be done, and includes compatibility information as well. This guide can be found in the links below.
Links
https://www.cisco.com/c/en/us/td/docs/security/firepower/quick_start/reimage/asa-ftd-reimage.html
https://forum.networklessons.com/t/reimage-cisco-firepower-to-cisco-asa/27428/2?u=lagapides