I would go ahead and say that in/of can be used interchangeably in this context.
Generally 'in' is the preposition of place/location and 'of' is the preposition of possession
In this case
"The "Conversions" section in the language specification." - place/location/position of "Conversions"
"The "Conversions" section of the language specification." - "Conversions" section belonging to "language specification"
Both of them sound about right.
But this is not the case usually, 'in' and 'of' are not interchangeable always. If you are interested to explore more about situations using 'in' and 'of' interchangeably, refer to this stack question, am sure it will help you a bit more on understanding the notion.
By preposition
Indicating a deadline or the end of a particular time period.
‘I've got to do this report by Monday’
- ODO
Until preposition and conjunction
Up to (the point in time or the event mentioned)
(as preposition) ‘the kidnappers have given us until October 11th to deliver the documents’
(as conjunction) ‘you don't know what you can achieve until you try’
- ODO
Common Mistakes in Business English notes:
- Use “by” when you refer to a deadline.
- Use “until” when you refer to the period of time before a deadline.
English With a Twist notes:
Until – describes a period of time before the deadline. In other words, up to a particular time.
By – is a time preposition and means “on” or “before”. It tells you when.
The key difference is that by focuses on the deadline while until focuses on the period before the deadline.
Here are your quotes, which I'll number for convenience:
- I've got to pay the money back by the end of the month.
- I've got until the end of the month to pay the money back.
- I put on an extra pair of socks. Until/By then me feet were freezing cold.
- I stood outside the cinema for an hour. By then my feet were freezing cold.
Example 1 focuses on the deadline itself (date of final payment), whereas example 2 focuses on the period prior to the deadline (period when payments are accepted).
Examples 3 and 4 with by speak of the time when the feet could be observed to be "freezing cold", whereas with until, they speak of the period of time when the feet were "freezing cold". There is a measure of intent that has to be inferred in these examples, about whether the end-point or the duration was the focus; it's not completely precise one way or the other.
The context of #3 suggests that the "freezing cold" applied prior to wearing the extra socks. The focus of the "freezing cold" sentence could be on the period prior to wearing socks (use until), or it could be on the time at which the socks were put on (use by).
On the other hand, the context of #4 suggests that the focus is on the time at the conclusion of the hour, so by is more appropriate. Although it talks about a time period, one's feet normally don't start off "freezing cold", hence the "freezing cold" reference applies to the end of the hour, not to the whole hour. Had the context sentence been that the person stopped standing outside after an hour, the inference would be stronger that they had concluded their period of having cold feet - the period then making until more appropriate.
Best Answer
Of the past is an adjectival phrase, but in the past is an adverbial phrase. So your first sentence, if you substituted one phrase for another, would have different meanings. To say that "phones in the past were landlines", which contains the omitted verb "used" before "in the past" does not suggest that modern phones are landlines, but "phones of the past were landlines" says that those which have survived in someone's basement still are landlines.
This is implicit in your second sentence fragment (which is not a complete sentence), since presumably the rest of the sentence compares transportation in the past to transportation today, and either discusses the differences between them or establishes similarities - but either way the two classes of transportation are assumed to be different. If they were not different there would be no point in comparing them. But "transportation of the past", such as horse-drawn carriages or steam-driven locomotives, has not changed today, although it may not be used much.