Qual è la differenza tra Previously e Earlier ?Sentiti libero di rispondere con un esempio.

I would say both sound fine, but using "previously" is more business-like. I would be more likely to say, "As discussed previously," in a work email, but more likely to default to saying "like I explained earlier" or "as we talked about before" when speaking with a colleague of equal standing.

Colloquially (eastern Midwest US), "earlier" can have connotations of being more recent than "previously" which is more vague. Your #2 sentence might be taken as slightly aggressive, like saying, "I just told you about this; why don't you remember?" However, that last sentence might be more specific to my region of the US.