I want update from 184.108.40.206 xiaomi.eu stable to 6.9.15 xiaomi.eu developer. I can update with this menu?If you mean by developer this weekly roms, in theory, wiping cache and dalvik is enough. If you'll have issue or wish to be sure wipe data also.
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Post log from TWRP..I download twrp from your site, reboot in recovery, format data, reboot in recovery again, same error 7 "could not extract cust in /cust".
I see that after second reboot in recovery, cust is not mounted, but even when mounted I have same error.
Flash this firmware, then it will receive the update OTA http://bigota.d.miui.com/V220.127.116.11.MXDMIDE/miui_MI3WMI4WGlobal_V18.104.22.168.MXDMIDE_2770e971bd_6.0.zip