before vs earlier

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. I have said it before.
    1a. I have said it earlier.
  2. I didn’t know that. You should have told me before.
    2a. I didn’t know that. You should have told me earlier.
    Which are the sentences correct?
2

All of them are possible. You would use ‘before’ in some contexts and ‘later’ in others, but there are some contexts which can take either.

3

Beeesneees,

  1. I wrote a letter before you arrive.
  2. I wrote a letter earlier than you arrive.
    Are these sentences OK?
4

No

I wrote a letter before you arrived.
I wrote a letter earlier.