They can mean the same thing, but it is subtle. For example, I might say, "Give my regards to your mother." What I mean is, "Tell your mother I said 'Hello.'" But, for example, in your opening sentence, if I meant, "I want to greet mt friends," I would never say, "I want to regard my friends." If I were speaking to a third-person, who might speak to my friends before I do, I could say, "Give my regards to my friends." Does that make any sense?