You can access and edit your device list here.
Category: pre-selected as 'Connected devices'
Model info can be found when you open your Fire TV Settings > My Fire TV > About > 'Device Model'
Check Model (listed right under About on About screen, example: Fire TV Stick 4K)
4. Model Release Date:
Check this page to decode your Fire TV or Fire TV Stick serial number.
5. Operating System: Fire OS
All Fire TV devices run on Fire OS (which is a heavily modified Android OS)
6. OS version: OS Version info can be found when you open
Settings > My Fire TV > About > “Device Model”
Check Software Version (listed to the right on the About screen, example: Fire OS 22.214.171.124)
7. OS Release Date:
Check this page for your Fire OS version release date.
This is an example how the final device adding screen would look like:
Please note: Your Fire TV will generally update to the newest OS version automatically in regular intervals, please verify the current OS version before every Run.