I have just searched for the usage of "until" and "by", and I was confused by these sentences. I've tried my best to tell the difference between them, and give my understanding in the bracket. Is there anybody who can tell me am I correct?
I've got to pay the money back by the end of the month.
【=pay before the end of the month】
I've got until the end of the month to pay the money back.
【=I don't need to pay it back any more, once I successfully shun the debt】
I put on an extra pair of socks. Until/By then my feet were freezing cold.
【until:my feet were no longer cold after I put on stocks】
【by:several minutes before I put on stocks I felt cold】
I stood outside the cinema for an hour. By then my feet were freezing cold.
【=in the end of the hour, my feet were cold】