Eventually I found here to seek a solution.
I flashed stock rom 6.7.246, but found the HDMI is not working:
After pluging-in hdmi cable, nothing showed up on the phone's screen, nor the tv.
Only on one of the TV, right after I switch the "Input HDMI" to the connected HDMI port (say, HDMI 3), the phone's screen changed to landscape, and the TV's screen will have the mirror of the phone's screen.
BUT regretfully, this kind of "mirroring" can last only ONE SECOND. Then phone's screen goes back to portrait, TV's screen goes back to "No Signal".
I did a lot of works too, to figure out why, including trying out other cutomized Roms, and some "hacks" claimed to be working to the issue (yes, it WAS a issue. I say WAS b/c those hacks were posted on 2011/2012). But none could cure my case.
It appears that it's not a hardware issue. So I'm seeking a way to rollback the 6.7.246 to GB. Since a lot of discussions have indicated similar HDMI problems happening only on ICS Roms.
I know it's dumb b/c there's saying that 6.7.246 is a one-way-ticket - it cannot go back to any GB roms, even any ICS roms prior to 6.7.232, say 6.7.2233.
But I found post in a foreign country's forum claiming there's a way to make such roll back to .902 using a thing "flashme" and some replacing tricks.
So I just come here to seek a simple answer:
A. Is there any other way to make HDMI working? like partially flashing any webtop image?
B. and furthermore, is it possible the method of "rolling-back" could work? I can give more details in this case.
Sure I prefer A anyway. I don't like the risky flashing work, if not forced to.
Thanks in advance.