Also, I want to know if such requirement of "a fundamental change of state " only applies to "by [date]", or there are other timeframes that require the corresponding verb to signify "a fundamental change of state"? I notice the example you gave in the quote about the "the scholarship" , which uses a timeframe "between 2000 and 2005". Besides, is "before [sth happened]" a timeframe that requires the verb in the main clause to represent a fundamental change of state?
Nah. "Before" just means "before", and so is equally capable of expressing simple sequences of actions. (e.g.,
I usually walk the dog before going to the gym.)
Take a look at some examples of "by (timeframe)". E.g., just search for something like "by Friday" or "by 1995" (with the quotes) on google, and then pay attention to the contexts in the search results.
With "by ____", you'll notice that _____ is consistently seen as some sort of cutoff date
by which something must be done (
You need to pay this bill by Friday, or late fees will be added).
Or, for retrospective things (like
New City had become the country's biggest city by 1905), it's a transition date, as explained earlier.
For some things, it's even both. E.g., when you say that a Pom is a throwback if it achieves the weight of 14 pounds
by the age of one year, that's both a transition point AND a cut-off date.
"Before" doesn't carry these connotations. It
can carry them, but it's much more versatile.
("Versatile" is not always a good thing; the downside of "versatility" is that there's more potential ambiguity in a statement. Not tested on the GMAT, but, just something to think about.)