UPDATE: Let’s start with disclaimer: Since my restless soul didn’t allow me to dismiss my watch issue, I decided to take a chance with my watch (without sufficient knowledge and suggestion from experienced member not to do it! I made a choice to gamble with my investment )
Thanks to this great community (the ones with questions and others with answers – in my case both very helpful) I found out, that Zgpax S99c watch is not so easy to brick😊. After a few try-and-error attempts, my watch today runs on KW88 firmware with TWRP and root access. Tried 6, 7 different firmware (kw88 different versions, kw99 different versions, Blitz…) but kw88 fits perfectly. The biggest challenge was root access, since all firmware I tried were operational (except Blitz – black screen but watch was operational) BUT with upside-down display and touch points on the screen on the right spots, not inverted. To fix that, access to build.prop setting “ro.sf.hwrotation” was mandatory. I finally made it with TWRP recovery for AllCall W1 from Ciro Danise - thanks a lot! (TWRP for kw88 kept rebooting to stock recovery and I didn’t find patched boot.img for it).
There is a small glitch when screen is about to turn off, a split second before that, screen is bright white and then turns off. If anybody have idea how to solve this, please let me/us know😉.
So after 2 days I can confirm ZGPAX S99c is running:
Firmware: KW88_CS1_B_GSM_PHT_20170518 (found on this forums, older because I needed one without BT calling)
TWRP and root: /thread/1765/twrp-recovery-allcall-w1
Battery life: maybe even slightly better than before
Heartrate sensor: working
3G: can’t tell since I’m not using sim
Watch Droid: perfect and rock solid! Not a single disconnection in 2 days
Other: everything I tried worked so far (ES Explorer, Setting Search,…) and of course
Eric’s Universal Launcher: without a glitch (thank you Eric for all your work).
Hope this can be of any help.