[G3 General] reb00tz:
I got it working!

Hi [MENTION=1069442]DomFel[/MENTION], [MENTION=1262674]kalunlee[/MENTION],

First of all, thank you both so much for your work and advice and help. Without which, I would not have dared to get the D857 and then tried to get it flashed to the D858HK.

I would like to state that [MENTION=1069442]DomFel[/MENTION]'s instructions are mostly correct for my setup, except that several files and certain bits were missing - likely the steps he/she (making no presumptions here) encountered were different to mine, hence the difficulties I encountered were not addressable by anyone up to that point.

Difficulties/differences from OP that I encountered:

LG FlashTool errored out using the OP files, stating that partitions were different, despite the ro.product.model change

this was resolved by utilising the required "flashing" DLL with some pre-set

XML setting files

that effectively force the LG FlashTool to run a blind flash, ignoring errors

originally found from this page, actual link here (password: 1xs4)

I suspect it is not the DLL that made the difference (between what was linked for download in OP), but the actual XML files that are provided vs. those that are automatically generated by FlashTool in the absence of the two files in the same location as the selected DLL

flash was actually (partially) successful up to the reboot, whereupon mobile got "stuck" at the blue screen with "Factory Reset 3", then "Factory Reset 2", then "Factory Reset 0"

clicked "C" beside the COM41 in FlashTool to clear the status (i.e. set back to "READY!"), then attempted battery pull and re-plug in with USB cable

the first time this happened, a complete re-flash took place, but the reboot ended up in the "MiniOS" with the auto-test (ATT mode)

FlashTool will repeatedly state that the flash failed as it failed to initialise the IMEI

pulled the battery and rebooted, but repeatedly got stuck in auto-test mode, finally found the solution here (specifically this post - i.e. press and hold the power button first, then tap the "Normal boot (+Power button)" option; I was stuck because I kept pressing the screen first then pressing the power button).

P.S. Note, as mentioned above, there was a total of three re-flashes taking place as I forgot to stop the FlashTool when pulling battery + re-inserting battery and USB cable; but as mentioned, it seems to have worked still, so maybe a 2nd re-flash is necessary to get it unstuck from "Factory Reset" mode).

In the interests of the time taken to download all the crud (particularly the D858HK TOT file), please find my contribution here (magnet links):

LG FlashTool v1.8.6.527 w/MegaLock.dll Replacement

"universal" LG G2/G3 DLL and "blind/forced flash" configuration files for LG FlashTool

D858HK v10d TOT file (i.e. LGD858HKAT-00-V10d-HKG-XX-SEP-15-2014-32G+0.tot)

And, separately, because it is not needed for the D857 to D858HK cross-flash, but once again, to side-step the slow download speeds for those adventurous enough to try:

LG FlashTool 2014 (build 03/07/2014) (vietnamese software, not to be confused with "official" LG FlashTool above, actually uses LGUserCSTool.exe to flash)

D858HK v10f KDZ file (i.e. D858HK10F_00.kdz) - as per OP, remember that this is currently not "rootable" as of writing this

P.S. I have not tested the v10f KDZ nor the FlashTool yet... Once I have gotten the phone completely set-up, maybe attempting to try using CWM or TWRP (anyone know of one that works for D857/D858/D858HK?), I might try upgrading piecemeal to keep root as per the instructions here.

Once again, thanks to [MENTION=1069442]DomFel[/MENTION], [MENTION=1262674]kalunlee[/MENTION], and woshilongbaobao over at GFan BBS.