Help All apps reversing to home screen/home screen cycles constantly

[Saberinsky]

Hi All. I have a S3 korean version SHV E210S initially running 4.0.4. After six months of use, WIFI kept dropping even when next to the router so I upgraded to 4.4.4
This was a bad idea and all apps were freezing and not working. So i tried to downgrade to 4.1.2 but it didnt work (magic string missing and unsupported version error on ODIN). I managed to flash 4.3 but now NO app works, even going to settings, the phone reverses to homescreen as if someone was pressing the back key. As soon as i touch an app, it flashes open and closes.
Left on its own, it cycles through all the screens constantly. Is this a hardware fault? How do I check?
It exhibits the same behaviour in safe mode. I havent updated any apps after flashing firmware

 

[Hadron]

If you've been flashing between very different versions (4.0 -> 4.4 -> 4.3) have you tried a factory reset? Certainly try wiping cache from recovery, but if that won't fix it a full reset is worth a shot.

 

[saberinsky]

Yes i have done the full reset/wipe cache in between flashing. But now its gone berserk, even during first use where you select language and then to wifi etc it keeps going back to the select language screen

 

[funkylogik]

Yes i have done the full reset/wipe cache in between flashing. But now its gone berserk, even during first use where you select language and then to wifi etc it keeps going back to the select language screen

You sure you've flashed the right firmware for your EXACT phone model version?

 

[saberinsky]

Yes 100% sure.

 

[saberinsky]

Any idea why cant i flash the older version 4.1.2? I have tried many times and it fails right at the beginning with the error msg "unsupported version"

 

[Hadron]

Odin is Samsung-specific, so as I've never owned one I don't think I can help with this. But we have a fair few Samsung owners around, so hopefully someone will be able to.