Is there any Difference between 'up to now' and 'so far' except to the condition when 'So is' is used for 'distance' in the sentence ? I would be greatfull if anyone would tell me,thanks
In most situations they are interchangeable. According to this NGram, so far seems to be significantly more common than up to now.
In situations where something is coming to an end, there may be a preference for up to now, whereas so far implies that the situation will continue:
Meals in the staff canteen have been subsidised up to now, but from January the subsidy will be withdrawn.
The festival has been pretty good so far- let's hope it stays that way!