Those two mean the same thing: the deadline is Friday. There's a slight difference in tone, though.
The first wording (doesn't..until) has a more relaxed tone; it's almost suggesting that a little bit of procrastinating is okay. The second wording (has..by) suggests more of a sense of urgency.
So, let's say it's Tuesday, and I'm working on a report. A coworker asks me out to lunch. If I think I can go to lunch and still make my deadline, I might say:
Sure, let's go. This report doesn't need to be ready until Friday.
but if I think that going out to lunch now means staying late on Thursday, I might be more inclined to say:
No, sorry. This report needs to be ready by Friday. Maybe next week.
That said, this is a somewhat subtle nuance, and the two situations wouldn't necessarily require those respective wordings.
Similarly, let's say I'm the boss, and I'm assigning the report to a subordinate, who asks me, "When do you need this report?" If I answer:
The report doesn't need to be ready until Friday.
that implies I don't need it right away. I might say that on a Monday or Tuesday, but I wouldn't say that on Thursday. However, if I say:
The report has to be ready by Friday.
that implies a more urgent sense in the matter, and perhaps someone will be in hot water if the report is late.
There is a huge difference between the two
May all your dreams come true.
is a wish for someone's dreams to be fulfilled, without any intervention by the listener.
Let all you dreams come true.
implies that the listener may be doing something which is stopping their dreams from being realized and they needs to stop doing that to "let" their dreams happen.
Best Answer
Definitely not.
I would use "This is not always used." when talking about something that is almost always used, but not always.
I would use "This is not used very often." when talking about something that is almost never used, but is used sometimes.