I believe you're referring to GameMaker Studio 2 (or possibly a specific executable like gamemaker.exe or a runner file) being patched to version 1001 (which typically corresponds to 2022.1.0.1001 or similar runtime versions in GameMaker’s numbering scheme).
In the context of Command & Conquer: Red Alert 2 - Yuri’s Revenge gamemdexe patched to version 1001 best
The file gamemd.exe is the core executable for Command & Conquer: Yuri’s Revenge I believe you're referring to GameMaker Studio 2
Scouring forums reveals a consensus: