The phone is back to life!
So, here is what I did: thanks to user stympy, who gave some valuable advise, and was actually on the right track.
The phones with a production date starting from 03.2014 have an updated PRELOADER. If you try to use flashing the PRELOADER of any other rom here on these phones, you'll end up like me.
The production date, I think, is printed on the battery (if you have a Chinese model at least).
YOU CANNOT FLASH A PRELOADER OF THE ROMS ON THE FORUM ON PHONES WITH A PRODUCTION DATE 03.2014 OR LATER (at this moment)
So, I found on a Russian forum (sorry XDA but for Lenovo there is a lot more to find on 4PDA than here), a backup of the correct,new preloader.
- I took the P780_S129_130710 ROM, and replaced the preloader.bin with the one in this rom.
- Next, deleted the checksum.ini file in the rom to avoid errors
- Open SPFT, selected the ROM, made sure PRELOADER entry was pointing to the correct preloader.bin
- USB disconnected, I clicked Download with DA DL All with checksum activated
- Plugged in USB
- Flashed without issue, disconnected, and voila, boot!!!
Well, that gave me a Chinese interface, but some screenshot tutorials enabled me to switch it to English.
I luckily took a backup with MobileUncleTools of my IMEI, since that was gone.
Phone seems to work normal, with 2 SIM cards, but a lot of Chinese bloatware.
While I was at it in SPFT, I tried to flash pre-rooted, or ROW versions, but that was unsuccessful so far. Always the good old 4032 error, although I updated the preloader, or some other failures.
However, the problem I'm trying to fight now, is the recovery mode. Can't backup (and not going to try flash ROM through recovery), since I can't mount /data, /emmc, and other crucial partitions. I'm using CWM. My goal is to flash the SLX ROM or any other rom with less bloatware, in English, and stable.
- P780_S135_130917_rooted_twrp_gapps + modified preloader
and works fine: had to manually link the UBOOT to the LK file (SPFT did not do it by itself)
- VIBEUI_V1.5_1419_5_DEV_P780_rooted_twrp_gapps + modified preloader
and works fine : same problem with UBOOT
- Some other (Chinese) versions. ALWAYS put in the preloader file I attached, and everything went smooth and OK
Decided to not use CWM anymore, it's buggy. I use the built in TWRP recovery, and that works like a charm. No issues whatsoever.
Decided to keep VIBEUI_V1.5_1419_5_DEV_P780_rooted_twrp_gapps, but my preferred one until now was just the old stock version.
Simple and good
I've attached the preloader.bin I used (use at your own risk!), I guess it might come in handy for all of you with the same problem
Note that this particular preloader worked for me on a Chinese model 4Gb, production date 15/03/2014
And thanks again to Stympy for all the help!