Rocky, will take the updates, but on reboot it ALWAYS reverts to the FIRST kernel that was installed.
It should boot the latest kernel by default.
Can you explain more, since I have both Rocky 8 and 9, and neither boot the old kernel. Maybe you have some specific configuration on your system. Was it upgraded/migrated from CentOS maybe? Or something else.
Otherwise, I don’t see how it can be possible on a default clean installed system.
Do newly installed kernels show up as boot entries? It might also be helpful if you can upload /boot/grub2/grub.cfg, and ls /boot/loader/entries.