Universal UI Features: 

-Start Screen
1. Enabled Achievement Button for every edition
2. Lowered Skin doll (1.12 Parity)
3. Reverted SignIn Button to match 1.12 style
4. Moved credit and version texts 

-Play Screen
1. Reverted Tabs to match the old-grayed tabs from 1.12
2. Removed Realms advertisements in 1.17
3. Fixed Create World Button And Add server offsets
4. Added Old Server tab (Long Lighted-Server buttons)
5. When you hover over the join button for featured servers you will notice a purple border has a ping display for the current server you pressed 

-Profile Screen
1. (SOON) 1.12 UI 

-Settings Screen
1. Removed Broadcast and subscription sections to Increase FPS in the screen
2. Fixed wrong offsets
3. Removed 5 toggles from Accessibility section (1.12 Parity)
4. Added old Resource pack Screen from 1.12 and completely removed the 1.16 - 1.17 resource pack screen 

-Containers/UI_Common
1. Java offsets to inventory cells
2. Edited X button to match Java offsets
3. Removed Center_Fold and instead added padding 1 pixel
4. Added Java highlight cell overlay for touch and win10
5. Added Crafting label near the 2x2 crafting cells (Java 1.8)
6. Unlocked win10 scroll bars to touch users
7. Completely deleted MinecraftTen font as it wasn't in 1.12
8. Persona screen fixed wrong offsets with minecraftten labels
9. Removed button offset 1 pixel down when pressing
10. Edited inventory_hold_icon so it will be seen for touch users
11. Edited container_scroll_background_image so it will match Java UI
12. No Item animations in hotbar
13. No vignette_renderer 
14. No flying_item_renderer
15. Edited trade_2 screen to match Java
16. Added panorama_overlay to every screen
17. Added 1.12 panorama
18. Added faster screen_animations for 1.17
19. Added big coin and player's packs banner (1.12)
20. Added red button for quit popup screen
21. Fixed offset in subpack screen
22. Removed black banners around texts in hud
23. Added Java hud
24. Added black bg for how to play screen (1.12)
25. Added sounds when you enchant an item ( Java )
26. Edited Emote wheel screen
27. Added Old Create World screen
28. Removed Realms adverts from Create World screen
29. Added Hide chat toggle to the chat screen just like 1.12
30. Added old achievements screen for 1.16
31. Added old text colors from 1.12 
32. Added old loading screen texts
33. Added old splash texts
34. Removed Skin doll head offsets 

1.12 UI Review:

creator: https://www.youtube.com/channel/UCUHU-gvZfn2VpjzCw7FmlSw