Thanks to the community!
Agree with provide more hints for newbie. In my case, i spent 2 days to figure out the pre-install steps on brand new Xperia X, its a bit lack of clue for me.

Some suggestions

• Add back up your TA partition warning in this post
  More clue for TWRP, cuz I think its requirement
• like command fastboot flash recovery ....img
• and key press to get in it (vol down + power)

In the end, I success by "wiping ART cache, cache, System, Data, and installing UT" twice. Even the guide are clear enough, I've still got panic several times during installation. Personally, I think the Sony unlock and UT installer's feedback is the most confuse part.