Can I use unreal as an external library?

i don’t understand, if is necessary the uproject file or no, if i build project like dll, after for init a project from another software , i need a uproject for open ?
if i want build myproject.uproject like dll and enable the library api, it is possibile give to another person my dlls file without uproject file and the person using my dlls for open myproject with Api ?

It’s here Box