How can I safely test custom ROMs on an obscure device?

I have a ZTE Blade A1 with pre-installed malware. I'm only able to identify and remove some of it. So, I want to delete everything on the phone and install a custom ROM. Unfortunately, I cannot find any ROMs which explicitly support the ZTE Blade A1. I've decided to try putting CyanogenMod on the device (or possibly something else), as it *does* support older versions of the ZTE Blade. My plan is as follows: 1. Create a backup of the existing ROM using ROM Manager 2. Run the device in recovery mode (using the default Android system recovery - CWM or TWRP do not explicitly support the Blade A1, so I won't risk using them) 3. Use the fastboot commands fastboot -w and fastboot update rom.zip to install the custom ROM 4. Restart the phone, and if it has stopped working, repeat steps 2 - 3 using the backed-up ROM from step 1 I've read up on using custom ROMs, but have found a lot of conflicting information. So, my question is: *Will this replace the pre-installed OS with a custom ROM? Is there a risk the phone won't be restored to its original state?* **Update:** I haven't been able to confirm whether the phone can be irreversibly bricked by installing a custom ROM. However, if anyone comes across this question wanting to remove malware from the ZTE Blade A1, I have posted a solution here .