As far as I know your license allows you to use any of the language versions up to the version number you are licensed for.
I typically use AUS language version, but in the past I have also installed INT, USA & UKI versions - all using the same language.
You can't change the language of Archicad at the touch of a button, but you can install more than one version at once.
You will need to rename the Program Folder after you install each one as otherwise Archicad will say it is already installed when you try to install a different version.
Give it a try and then post back if you are having any problems.
I currently have many versions and builds loaded and also a USA version for 21.
You can see the ones I have re-named, and to run them I just run the program file in that folder.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11