Can i download code at runtime. (DLL or script or package)

Hi, I have a game in which i want to download a functionality at run time. The functionality should be present in a DLL. so can i download this dll at run time and use this functionality ?

In making dll, i am having dependency issues. The script has many external dependency (plugin and even on the game play code). If i create a dll and separate it from project , all the other scripts which has its dependancy starts giving error.
so is there any way i can ignore these errors and create a build of it and at run time i want these dependencies to connect and work as intended . Is it possible to achieve it ?

My app is present in ios and android app store.