In early History concerts, MJ was trying to do more parts live.
DANGEROUS
In the first two concerts, he sang the "Dangerous, you got, you got ... my baby!" part live.
Prague:
https://youtu.be/Wx7oVI1fZxc?t=5616
Budepest:
https://youtu.be/XYIVQUPeOgo?t=5020 , only the second "dangerous" was live.
BTW in Ostend, MJ did the entire rap part live, but that's not a "subtle" change.
YANA
In Prague (first concert), MJ sang more live parts of YANA, he started live right after the key was raised the second time. Unlike the later concerts, where he started live after the long "in my heeeeeaaaaarrrrrt". But even though he started live earlier, he still didn't sing the long "heart" part, he was just ad-libbing randomly.
Prague:
https://youtu.be/Wx7oVI1fZxc?t=2415
STRANGER IN MOSCOW
In the first several concerts, you can hear the backup singers singing the first few lines of "Stranger in Moscow" on top of the playback, but usually the live backup vocals were cut off after the second line.
Prague:
https://youtu.be/Wx7oVI1fZxc?t=1408
Budapest:
https://youtu.be/XYIVQUPeOgo?t=1235
Bucharest:
https://youtu.be/dG_Zi-2TCZQ?t=1271
In the above three concerts, you can clearly hear the live "Mask of life, feeling insane", but starting from the second line "Sunny days seem far away", you can't hear the live vocals anymore.
I didn't find the footage of Warsaw concert, but I can't hear any live backup vocals in the Zaragoza concert which is after that.
Zaragoza:
https://youtu.be/Mpko8m5Re_k?t=940
In Kuala Lumpur Oct 27 concert, you can hear the first two lines of backup vocals being live, but starting from the third line "Stalin" it's pure playback.
https://youtu.be/S4a4sJ7ldA8?t=1206
In Kuala Lumpur Oct 29 concert, you only hear the first line live, but it's very quite, starting from the second line it's pure playback.
https://youtu.be/DmcHZMyAnc0?t=1337
TWYMMF
In Amsterdam 1996, Zaragoza, and Tunis, MJ did the ending part live, just like in previous tours.
Amsterdam:
https://youtu.be/pglkVnwlsx0?t=2508
Zaragoza:
https://youtu.be/Mpko8m5Re_k?t=2168
Tunis:
https://youtu.be/Q6o5jgVDFzw?t=2235
Some fans say that these were fails, but I don't think so. I think MJ were just trying things out during the first few concerts.
The following one, however, were indeed fails to me.
BEAT IT
In Sydney, MJ did this song completely live. There isn't any footage of the entire performance, but we had a mashup video mix containing two "Beat It" clips.
https://youtu.be/J5JuVuDz56w
So the structure of Beat it in History Tour is:
Cherry Picker Intro,
Verse 1, Verse 2, Chorus 1,
Verse 3, Verse 4, Chorus 2, Chorus 3,
"Beat it" Echo, Guitar Solo,
Chorus 4, "Ho! Ho! ad-libs", Chorus 5, Chorus 6,
Call & Response with audience "Haaa! Haaa!",
Dance Routine,
Chorus with ad-libs 7, 8, 9,
Outro.
In other concerts, MJ would lip-synch until Chorus 5, which is the second chorus after the guitar solo, and he would start singing live after the long "ho! ho!". You can check the video of Munich concert,
https://youtu.be/Xz-WKZnK_5Y, where he started singing live from 3:42. The backup singers would sing live starting from Chorus 7, ie after the dance routine.
In this concert, the first clip from 0:00 to 0:15 is the chorus before the Call and Response session, so the chorus being performed is Chorus 6. It's true that MJ's lead vocal of this part is always live. But the backup vocals in other concerts were still playback, here they were also live.
But the second clip, from 0:15 to the end, is the chorus before the guitar solo session, which is Chorus 3. Chorus 3 was never performed live, nor was the "Beat It" Echo effect session and the "tsch tsch" sounds. This proves that this concert is unique.