"up to" and "until" are similar in use, for example: - We can stay up to/until 11pm, Here the two expressions are - referring to time. "as far as" is used like this: - As far as I know the library is closed today because of the holiday. Here "as far as" - means "the extent of (my knowledge of something)"

"Up to" is a useful idiomatic expressin in English. If, for example, you ask, "what have been up to?, it means, "what have you been doing?" If you say, "he is up to no good," it means "he is acting with bad intentions." If you say, "it is up to you," it means "it is your choice." If you say, "you have up to Friday to make up your mind," it means "you have until Friday..." Good luck learning English, Richard