Update c65

[ertnex]

Hi everyone,
This is my first thread here, and I wader if someone can give me some
I bought my device (c65 AfterGlow) on Amazon.it, and I made the update from the site https://onyx-boox.com/support/firmware-android/ that works fine. Stumbling around I found also an update here http://www.onyx-international.com.cn....php?serial=43 that seems to be more recent than the other one, but I couldn't install it on my device, because it says that the package is not valid.
Now, as I understand, the latest one is for the c65ml, and checking in the system information it seams that my model is c65ml_artatech, so I'm a bit confuse
The reason why I'm struggling with this, is that, after unzip the update.zip from the second link, and checking in the system's app, I found the google framework service and the vending apk, so I figured that on this device, the market should be available. In the first moment I thought that maybe the update I've already done excludes the latest one, so here my questions: are there different kinds of c65 afterglow? Is there a way to downgrade the firmware so I can try to install the other one?
In the meantime I've installed the amazon app center, that works for the few apps compatible with android 2.3. I also try to install an old google service framework and the market (searching around), that let me log in and search for the apps but it crash at the end, so is pretty useless .
Not that I need all of this to read a book, but I'd like to try to get the best from my device.
Thank's for every clarification you may give me.
P.s. I try to find a similar topic to not open a new one, but I couldn't find any.