The most important thing for the player is that the compatibility with previously saved games is not affected.
It also rarely happens that the save format changes slightly, but the ability to load a game from an older version is preserved!
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HoMM3 HD 4.200 RC1
4.100 RC1 -> 4.200 RC1 (05/01/2016)
[-] bug: with varying probability (on some systems up to 100%), the game could close upon startup with the message "Unable to initialize resources - possible disc problem."
[ ] Improvements and bug fixes in RMG settings.
HotA:
[!] Attention! Network play in HotA with HD+ is only possible if all players use 4.200 RC1 or higher (the save format has not changed).
[-] Fixed known bugs in HotA.
[+] Simultaneous turn is available for any number of players of any colors!
[+] New displayed timer!
[ ] Changes for compatibility with the future version of HotA.
Added 11 hours 9 minutes ago
HoMM3 HD 4.200 RC2
4.200 RC1 -> 4.200 RC2 (05/01/2016)
[-] minor fixes