I assume you mean "add-ons"? All add-ons have to be built (compiled) specifically for each version of AC, as they utilize a variety of common information. So, you cannot simply copy an add-on from AC 20 to AC 21 and expect it to run. The developer would have to recompile it for AC 21.
One of the forum moderators
AC 26 USA and earlier • macOS Ventura 13.4, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB