You can try to login to bootrom and set up the previous version as first at boot up. You can check the upgrade guide - the section that refers to bootrom - to understand how the settings should be made. Check the link below, chapter 6.
http://support.huawei.com/enterprise/en/doc/EDOC1000136580?idPath=7919710|21432787|7923148|22318718|6078839
Step 9 Enter 4 to set the loaded system software as the startup program.
Enter your choice(1-7):4
Startup Select
1. Display Startup
2. Set Boot File
3. Set Config File
4. Startupfile Check Manage
5. Set Startup Waiting Time
0. return
Enter your choice(0-5):2
Select Boot File
1. Flash
0. Return
Enter your choice(0-3):1
NOTE: Boot file must be .cc or .CC
Current boot file: flash:/AR1220-V200R008C50SPC500.cc
Press ENTER directly for no change.
Or, please input the new file name: flash:/AR1220-V200R008C50SPC500.cc
Save the bootfile name: flash:/ AR1220-V200R008C50SPC500.cc ? Yes or No(Y/N)y
Save load state word...OK!
Startup Select
1. Display Startup
2. Set Boot File
3. Set Config File
4. Startupfile Check Manage
5. Set Startup Waiting Time
0. return
Enter your choice(0-5):0