It seems to me that these simple past forms, with certain adverbs, such as "fós", can correspond to English present perfect (have/has + past participle) eg "Has she reached the college yet?", particularly in British English. This alternative is generally rejected in these exercises.
Such translations should certainly be allowed, since they are often the most natural option in English, as you say. 'Has she reached the college yet?' sounds much better to me than 'Did she reach the college yet?' If you report such oversights, they will probably be corrected.
I have put in a report. It's worth noting that in the very next question after this in the sequence an English sentence with the "have" form was translated by an Irish simple past!
The English present perfect is often translated by the Irish simple past; the Irish perfect has a narrower usage than the English perfect.
Does this mean physically reach the particular college, or does it mean get to college (attending, etc.)?
Since "sroich" can also mean "attain," could this sentence also suggest that she has "attained a place" in the college?
No — “Has she attained the college yet?” ≠ “Has she attained a place in the college yet?”.
“Still” implies that she has not completed reaching the college, but “did” puts the reaching firmly in the past.
Where I live, we would also use "reach" to mean she got them on the phone-- would that also work in Irish, or is it only about getting to the place?