I used stock rom to downgrade my mibox 2 to 1.3.112d (to system 1) then rooted it with 360 root.
On MDZ-09-AA, I flashed a modified mirecovery:
Then I entered recovery and can see that my recovery has been reduced from version 6 to version 5.
Then I reboot to system 2. (black screen)
Then I cut the power and reentered recovery, I then saw the recovery was back to 6.
Then I reboot to system 2 again, now this time, I can enter system2. And the system 2 is 1.5.8
Then I reboot to system 1, system 1 is still 1.3.112d.