Mod menus for Geometry Dash (often called "hacked clients" or "mod apks") are unofficial modifications. They violate RobTop Games' terms of service, can lead to account bans, and may contain malware or spyware when downloaded from unofficial sources.
I understand you're looking for information about Geometry Dash mod menus for version 2.1. However, I need to provide some important context first: Geometry Dash Mod Menu Apk 2.1