The latest version of Sonic Frontiers is v1.42, but some categories use v1.40 instead.
These are the notable differences between them:
Early Cyloop is only possible on v1.40.
In Another Story, the Tax Evasion glitch is only infinite in v1.40.
In Another Story, Sonic's attack stat is higher in the Koco Trials in v1.41 and later.
In Another Story, Knuckles' glide has a wind-up animation that only exists in v1.40.
When dying in Cyber Space and respawning at the start of the level, the timer will reset in v1.41 and later (except Cyber Space Challenge), but not in v1.40.
For these reasons:
For any categories that don't get the blue emerald in Kronos Island, such as Any%, you should use v1.40.
For Another Story categories, you should use v1.42.
For Cyber Space ILs, using either version is fine, but v1.42 is more convenient when doing multiple attempts.
For any other categories, it doesn't matter what version you use.
Note that, on console, you can only downpatch to v1.0, but that isn't useful. As such, all console speedruns need to be done in v1.42.
Downpatching to v1.40 isn't particularly intuitive, but you can do it by using the following steps:
Press Windows key + R to open "Run".
Paste "steam://open/console".
Go to Steam and get to the console window (on the far right).
In the console, paste "download_depot 1237320 1237321 1729447390251868694".
Wait for it to download.
Find the files, which should be in Steam\steamapps\content.
Move the files to wherever you want them to be.
Create a .txt file called "steam_appid.txt" in the same folder as the .exe.
Write "1237320" in the text file and save.
Copy the files from your original Sonic Frontiers installation, and do not select replace files.
This will give you a separate install of Sonic Frontiers v1.40.
We recommend making a desktop shortcut for the new installation, as launching the game through Steam or HedgeModManager will always launch the most updated version of the game.