Just curious if possible to install a different version of dos on arca?
Yes. it is rather easy, as I remember. I don't remember the exact steps, and it was MANY years ago when I played with that. You do NOT replace what gets installed. You set up an image, and boot from that. It can be any DOS (possibly only MS or IBM versions, I never tried FreeDOS, or any others).
First you need to have DOS/WinOS2 installed, and working. Many newer machines don't have BIOS support for that. ArcaOS 5.1, in UEFI mode, will have better support for DOS/WinOS2, when it becomes available. Then find the help for how to boot DOS from a diskette drive. The image needs to be of a diskette boot, then you tell it to boot from the image file, rather than from a diskette.
IIRC, the DOS version installed with later versions of OS/2 (including eCS and AOS) is IBM DOS 5.0, with fixes. There is a newer IBM DOS 7.0, which has even more fixes. I have still got an image of DOS 7.0, but I haven't bothered with it for a lot of years. I seem to recall giving up on MS DOS, of any version, before machines eliminated the required BIOS support.
Then comes the question: Why do you want a different version of DOS, which you can set in the settings, if you have a program that doesn't like DOS 5.0? That makes DOS lie about what version it is.