config -x /boot/kernel/kernel|fgrep COMPAT
). So if you pkg install compat11x-amd64
on the 12.x system, the ctld(8) binary copied from your 11.x machine (or from an 11.x installation medium (for the same machine architecture)) should run... Which means that the program itself runs, but does not necessarily mean that the 12.x kernel behaves as expected because only the newer ctld(8) of the same OS version does what the new kernel needs to behave as expected.