Versions of what?
- Linux kernel -
uname -a(manpage) - application - usually
<AplicationName> --version(e.g.firefox --version) - Manjarno branch -
pacman-mirrors --get-branch(ref) - version x branch
But I think the problem is updating vs. flushing. Have a look at this thread.
There is no way to find out from a running system which image (stable and unstable branch) was used when flashing, I’m afraid.