Translation:A quarter to nine.
my native language is Dutch and we say 'quarter to...' so for me there's nothing wrong with it. Plus I believe some English speaking folks also use it. Still, it's not always about translating it correctly, I already think Duolingo focusses too much and too often on getting a grammatically correct answer in (American) English. That's all fun but that doesn't teach you the literal meaning of the Chinese sentence, which is very important if you want to truly understand this language.
A literal translation of the first is "nine awaiting a segment" (imagine the clock face as a pie with four equal segments) its used obviously here to tell the time i.e. "a quarter to nine". Rearranging the Chinede to form your second combination you get "awaiting segment nine o'clock" Chinese works with implied articles and context and a native speaker will add in implied words until it makes sense. So here it would imply "in a quarter of an hour it will be nine o'clock".
As a preposition, "till" is synonymous with "to;" as a conjunction, "till" is synonymous with "until" (but is not a shortened version of "until," as "till" was already a word in its own right for several centuries before "until" became a word). "A quarter to nine" and "a quarter till nine" are synonymous, and both phrases are correct.
In this sense of the word, "til" (without an apostrophe) is a variant spelling of "till;" as such, "a quarter til nine" is correct as long as "til" is an acceptable variant spelling of "till," but some people regard "til" as an incorrect spelling rather than a variant spelling.
"'Til," with an apostrophe, is indeed a shortened version of "until," but that's a different word with a different history, and yes, some writers drop the apostrophe, even when using "til" in its much more recent sense of a so-called "poetic abbreviation" of "until."
My understanding (possibly wrong) is that 差 is also "lack," and the role it plays here is like "menos" in Spanish, i.e. "nueve menos quince," or something like "it's lacking fifteen minutes to be nine o'clock." Very awkward in English, of course, but it works in Spanish or Chinese.
Many Chinese characters can have multiple meanings depending on the context. The dictionary hints don't always show every meaning that a character might have. When it comes to time, it might help to think of 差 as "less than" or "minus".
"9:00 minus a quarter (0:15) " = 8:45
"a quarter less than 9:00" = 8:45
"It's a quarter to 9:00" = 8:45
Exactly. This is not an English course so let's not expect that all 27,347 variants will show up here. Let's pick the most common way to say this in English to prove we've understood the Chinese; and move on.
Else we'll be here till next Christmas debating 'quarter to nine, 'quarter of nine', 'eight forty five pm', 'eight forty five am', 'sixteen hundred forty five hours', 'fifteen minutes to nine in the morning', 'fifteen minutes to nine in the evening', 'five minutes past eight forty in the morning', and two dozen thousand other grammatical gems because we are trying to learn Chinese? Eh?