I was thinking that flashing via adb over the actual ZTO fw should keep this CSC, then I'll be using the beta and when stable releases I just need to flash stable FW via adb again to keep files, settings and CSC, that shouldn't work?Brazil here too.
1 - you have to install a ROM from a region that supports beta program (India for example). After that, of course your CSC will change.
2 - When the stable version is released, you will have to install it the same way you installed the beta, via ADB. Being in the stable version, you will receive updates for the region your ROM is in.