I can get into recovery mode, but nothing more. If allowed to try a normal boot, then it will either stay on the "Karbonn Smart" logo screen forever and ever amen, or it will APPEAR to boot, but once it reaches the lock screen it dies on its arse. The best-case is that the lock screen will stay up for about 3 seconds, then the screen will go black for another 3 seconds, and then we go back to the lock screen and the process repeats. OR, the lock screen comes up, 3 seconds, and then we go back to the bouncing dots loading screen forever and ever amen.
I tried a hard wipe from recovery mode - it's made absolutely no difference.
This is a stock phone which has only ever received the OTA updates; I've never rooted it, I don't have a custom recovery installed, and I've never used ADB before today.
I've downloaded a number of "stock ROMs" for this phone, but none of them actually work for me; it doesn't seem to matter whether I try to install them through Recovery mode\Apply update from ADB, or put them on the SD card and try "Apply update from SD card". For most of them, I get the error "failed to verify whole-file signature" and it won't install; I tried to install the stock file from https://forum.xda-developers.com/cro...links-t3287707 but that doesn't get me much further; The error becomes
"Package expects build thumbprint of 6.0.1/MMB290/2459718:user/release-keys or 6.0.1/MMB29K/2419427:user/release-keys; the device has 6.0.1/MOB31E/3142026:user/release-keys"