By (+ a time) = not later than:

I sent the letter to them today, so they should receive it by Monday.
(= on or before Monday, not later than Monday)
We’d better hurry. We have to be home by 5 o’clock.
(= at or before 5 o’clock, not later than 5 o’clock)
Where’s Sarah? She should be here by now.
(= now or before now – so she should have already arrived)

We use until (or till) to say how long a situation continues:

‘Shall we go now?’ ‘No, let’s wait until (or till) it stops raining.
I couldn’t get up this morning.
I stayed in bed until half past ten./ I didn’t get up until half past ten.

Compare until and by:

Something continues until a time in the future:

Something happens by a time in the future:

David will be back by Monday.
(so he’ll be back not later than Monday)
I’ll have finished my work by 11.30.
(= I’ll finish my work not later than 11.30.)

It’s too late to go to the bank now. By the time we get there, it will be closed.
(= the bank will close between now and the time we get there)
(from a postcard) Our holiday ends tomorrow. So by the time you receive this postcard. I’ll be back home.
(= I will arrive home between tomorrow and the time you receive this postcard)
Hurry up! By the time we get to the cinema, the film will already have started.

You can say ‘by the time something happened’ (for the past):

Karen’s car broke down on the way to the party last night. By the time she arrived, most of the other guests had left.
(= it took her a long time to get to the party and most of the guests left during this timei
I had a lot of work to do yesterday evening. I was very tired by the time I finished.
(= it took me a long time to do the work, and I became more and more tired during this time)
We went to the cinema last night. It took us a long time to find somewhere to park the car. By the time we got to the cinema, the film had already started.

Also by then or by that time:

Karen finally arrived at the party at midnight, but by then (or by that time), most of the guests had left.

used to + infinitive is only used in the past: it has no present form.
We use it to talk about past habits and states which are now finished’

To talk about present habits and states, we usually just use the simple present tense

In a formal style, used to can have the forms of a modal auxiliary verb (question and negatives without do)

Did you use to play football at school? (informal)
Used you to play football at school? (formal)
I didn’t use to like Opera, but now I do (informal)
I used not to like opera, but now I do (formal)
(A contracted negative is possible: I usedn’t to )

I lived in Chester for three years
(not I used to live in Chester for three years)
I went to France seven times
(not I used to go to France seven times)

After be used to, we use a noun or an -ing
The meaning is quite different form used to + infinitive
If you say that you are used to something, you mean that you know it well
You have experienced it so much that it is no longer strange to you

be used to + noun

I’m used to London traffic – I’ve lived here for six years
At the beginning. I couldn’t understand the Londoners, because I wasn’t used to the accent

be used to +V- ing

I’m used to driving in London now, but it was hard at the beginning
(NOT I’m used to drive..)
It was long time before she was completely used to working with old people